Question

No estaban seguros de que el internet _[blank]_ bien.

Answer 1

Answer:

Se conectara.

Explanation:

No estaban seguros de que el internet se conectara bien.

Answer 2

Answer:

Explanation:

In this case, we would need to check who's the subject of the sentence.

(Ellos) no estaban seguros de que el Internet ________ bien

"Que" is a connector between phrases, like English's "that". This means that we are in front of a complex sentence. In this case, we need to ask WHO (question for the subject) is "connecting"

Who is connecting? The internet.

The internet is a 3rd person singular, so that means that it is "se conectara"