In the following question, out of the four alternatives, select the alternative which will improve the bracketed part of the sentence. In case no improvement is needed, select "no improvement".
She glanced back to make sure she (wasn't to be) observed.
Correct Answer: wasn't being
‘Wasn’t being’ uses the negative past continuous form of ‘be’, which signifies an action that was started previously and is still continuing.
In the sentence, she started the action of glancing back previously which was still continuing.