Fourteen questions in the three things this section actually asks, which are less alike than they look.
Five on conventions. A sentence with a fault in it, and the question of which change repairs it. The comma splice, the fused sentence, the fragment, subject–verb agreement across an interrupting phrase, a non-essential clause that needs its pair of commas. These are rules, not judgement, and the list of rules that matter is short and finite — which is why Conventions is nearly two fifths of the section and the most reliably winnable part of the whole test.
Two of them are worth naming here. The fragment question is a clause with a subject and a verb that still is not a sentence, because it opens with Because — and one of its wrong options replaces Because with Although, which swaps one subordinating conjunction for another and leaves the fragment precisely as it was. The comma-splice question offers the right conjunction on the wrong side of the comma.
And one question turns on something a student outside the United States has no reason to know: the team of researchers… were ready is unremarkable British English, and wrong on an American test, which follows the grammatical number of the collective noun. The explanation says so rather than leaving you to guess.
Five on production of writing. Should this sentence be kept or deleted, where does this one belong, which sentence best closes the paragraph given a stated purpose. All four options are accurate every time; only one does the job the question named. That is the format's whole idea, and the habit it builds — read the stated purpose, then test each option against it, and never against whether it is true — carries straight over to the SAT's rhetorical synthesis questions.
Four on knowledge of language, which on the ACT mostly means concision. At this point in time, the reason is because, each and every, in my personal opinion I think — the test has a consistent preference for the shortest version that keeps the meaning, and a great many wrong options exist only to add a phrase that repeats one already there. When two options say the same thing and one is shorter, the shorter one is nearly always right.
Two things about the real section that this cannot show you.
The first is NO CHANGE, which on the real paper is one of the four options and is correct about as often as any other. Students who assume a question implies a fault talk themselves out of it and lose roughly a quarter of the section. The format here asks "which change makes it conform" and keeps "No change is needed" among the options, which tests the same nerve.
The second is the layout: the real section shows four options differing only in a mark of punctuation, and the automatic checks that guard every bank here strip punctuation before comparing options, so four such choices read as one answer repeated four times and the material is refused. Punctuation questions are therefore set in words. The judgement is identical and arguably harder — you name the repair rather than recognising a shape — but the paper will look different on the day.
And the thing no question bank can give you: thirty-five minutes for fifty questions, which is forty-two seconds each. Pace is this section's real difficulty. Take a timed full-length section from ACT's own free practice material before you decide how ready you are.
"Because the storm brought down three transmission towers on the ridge above the town." Which change makes the sentence conform to the conventions of Standard English? — A clause opened by a subordinating conjunction is dependent and cannot stand as a sentence. This one has a subject and a verb and still is not a sentence, which is what makes fragments hard to see: length is no protection. Replacing "Because" with "Although" swaps one subordinating conjunction for another and leaves the fragment precisely as it was.
Read this sentence. "The team of researchers, including the lead scientist and two of her graduate assistants, were ready to begin the experiment." Which change makes the sentence conform to the conventions of Standard English?
Change "were" to "was".
RULE: a verb agrees with its subject, and a parenthetical insertion never changes the subject's number. The subject here is "the team", singular; everything between the two commas is an aside. Like "along with" and "as well as", the word "including" does not build a plural subject — only "and" does. A note worth having if you learned English outside the United States: British usage often treats a collective noun such as team or government as plural, and "the team were ready" is unremarkable in London. The ACT is an American test and follows the grammatical number of the noun, so "was" is the answer here. Deleting the comma after "researchers" breaks the pair that marks the aside — those commas come as a set. Changing "including" to "which included" is perfectly grammatical and changes nothing about the fault, which is the verb. "No change is needed" accepts the plural verb.