Concept:In reported speech, a past tense reporting verb often changes present modals like
can to their past forms, such as
could.
Explanation:The sentence uses a past reporting verb:
I told them.
It also contains
I would come back, where
would is the past form of
will.
This shows that the whole situation is being reported from a past point of view.
The time clause
as soon as I _____ must also follow the past context.
The modal
can changes to
could when used after a past tense verb in reported speech.
Option A,
should, does not express the same idea of ability or possibility in this context.
Option B,
can, is a present form and does not match the past tense reporting.
Option D,
will, is also a present form and is not correct after the past tense
told.
Only
could correctly completes the sentence in the past tense.
The completed sentence is:
I told them I would come back as soon as I could.Answer:C. could