Question

All banks __ (open) on the first and the third Saturday .​

Answer 1

$<font color=blue>$

♕ . All banks $\underline\red{are~open}$ on the first and the third Saturday .

Answer 2

All banks open on the first and the third saturday..

Explanation:

It will remain (open) in blank..because according to simple present tense..We are not needed to add s/es in the verb if the subject in the sentence is plural..

And here also in the given sentence..the subject (Banks) is plural..

Hope it helped u..

Please mark me as brainlist.