Select the most appropriate option that can substitute the highlighted segment in the given sentence. If there is no need to substitute it, select ‘No substitution’.
Alice won’t be coming to the concert as she was ill.

Correct option is B

The correct substitution of the highlighted words is (b) she is.
Explanation: The main clause “won’t be coming” refers to a future decision/state.
The reason clause introduced by as should express the present/continuing cause for that future decision.
Saying “as she was ill” suggests a past condition that may no longer hold, which clashes with the implied present cause.
Therefore, “as she is ill” keeps tense consistency and accurately states the current reason for her future absence. Option (c) “she is going to be” predicts a future illness (odd and speculative), and option (d) “she will be” also forecasts illness, not a present cause. Hence, (b) is correct.
Grammatical rule used:
· Sequence/consistency of tenses: Subordinate clauses take the tense that matches the time of the idea they convey, not necessarily the tense of the main clause. Present causes for future outcomes generally use present tense in the reason clause (e.g., I won’t travel as I am unwell).
· Causal conjunctions (as/since/because): When giving a known or current reason, present simple is standard.
Example: They will cancel the picnic as it is raining. (Present cause for a near-future decision.)
Information booster / exceptions: In reported speech or clearly past-time narratives, backshifting to past is normal (e.g., She didn’t come as she was ill yesterday). But for future plans with a current cause, use present in the reason clause.