my mom went to the grocery store. she forgot her purse...

a)comma
B)and
c)or
d)but
e)because

but

Which word do YOU think you should use?

I'll be glad to check your answer.

B)and

My mom went to the grocery store because she forgot her purse.

The correct answer is option e) because.

In this sentence, the word "because" is used to explain the reason why your mom forgot her purse. It indicates a cause and effect relationship between going to the grocery store and forgetting her purse.