My mother remarked that it was high time we … preparing supper.

Analyze the question The sentence uses the structure "it is (high) time + subject + verb". Here it is reported speech ("my mother remarked that it was high time..."), and we must choose the verb form that fits.

Explain the concept After "it is time / it is high time / it is about time", English uses the simple past tense to talk about the present or future. The past form does not refer to past time. It shows that the action is overdue or should already have started.

• It is high time you went to bed.
• It is time we left.

In reported speech, "it was high time" is already in the past, and the verb after it stays in the simple past: "it was high time we started."

Step-by-step solution

1. Identify the structure: "it was high time + subject (we) + verb".
2. Check the options: • A. were starting: past continuous. Not the standard form after "high time". • B. had started: past perfect. This would mean the action was already finished, which contradicts "high time" (the action is overdue, not done). • C. should start: "it's high time we should start" is sometimes heard, but it is not the standard idiom for this exam pattern. • D. started: simple past. This is the correct idiomatic form.
3. The sentence becomes: "My mother remarked that it was high time we started preparing supper."

Correct answer: D (started)

Tip: Memorize the pattern "It's (high/about) time + subject + simple past". Whenever you see "high time" in WASSCE, JAMB or NECO, go for the simple past form, unless the options include it in a different standard form. Remember that the past tense here carries a present or future meaning.