6. He can sit and read for hours at a stretch. (Choose correct meaning of the idiom 'at a
stretch'.) *
a) continuously

b) repeatedly
c) oftenly
d) sometimes

The correct meaning of the idiom "at a stretch" is "continuously".

In conclusion, the correct option is A.

Read related link on:

link

continuously

Explanation:

The idiom "at a stretch" as used above implies that he can read continuously without stopping.

Analysing other options

1. Repeatedly: When an action is being repeated, it means there's a stop before the action is eventually continued

2. Oftenly & Sometimes do not describe continuous actions.

Hence,

The first option (continuous) answers the question and it can be used as a direct substitute of the idiom.