Modal + perfect infinitive (logical deduction about the past): Improve the sentence to express that it probably did not rain. Original sentence: "The crops are dying; it must not had rained." Choose the option that makes the sentence correct.

Given data

• The speaker infers a past non-event (no rain) from present evidence (crops are dying).

Concept/Approach
For deductions about the past with a modal, use must + not + have + past participle → "must not have rained". "Must had" is ungrammatical.

Option analysis
C. "must not have" → leads to "must not have rained" → correct. ✔A → wrong auxiliary sequence.B/D → wrong aspect/meaning (present state or passive progressive).E → original is incorrect.

Corrected sentence
"The crops are dying; it must not have rained."

Common pitfalls
Confusing have (perfect marker) with had (past of have) after modals.

Final Answer
must not have