Select the most appropriate option to fill in the blank.

______ did she open her lunch box than everyone gathered around her.

No sooner

The most appropriate option to fill in the blank is No sooner.

• As soon as and just as both mean immediately after something happens. However, no sooner is more emphatic and suggests that something happened very quickly after another thing happened.
• Hardly means almost not at all. It does not make sense in the context of the sentence because it does not describe how quickly everyone gathered around her.