Verbs

Step 1: Understand the context of the sentence. The sentence says there are plenty of dresses already, which suggests that buying more is unnecessary or inadvisable, not forbidden.
Step 2: Analyse the modal verbs.
will not — simple future negation, does not fit advice.
must not — expresses strict prohibition, too strong here.
may not — expresses possibility, incorrect meaning.
should not — expresses advice or recommendation not to do something.
Step 3: Choose the most suitable modal. Since the sentence gives advice based on the situation, should not is the correct choice.
Hence, the correct answer is

Step 1: Recall the use of modal verbs with time reference.
Would not / wouldn’t is commonly used to describe a habitual action in the past.
Past habits must be followed by a past time clause (e.g., \emph{when he was a kid}).
Step 2: Analyse each option.
(A) Correct — past habit + past time reference.
(B) Slightly awkward but acceptable in informal usage; meaning is still clear.
(C) Incorrect tense agreement, but focuses more on tense mismatch than modal misuse.
(D) Incorrect — “wouldn’t” (past habit) cannot be used with “will” (future tense). This is a clear misuse of modal verbs.
Step 3: Identify the clearly incorrect modal usage. The combination \emph{“wouldn’t … will”} is grammatically invalid.
Hence, the incorrect sentence is