Answer:
Explanation:
In this case, we would need to check who's the subject of the sentence.
(Ellos) no estaban seguros de <u> que </u> 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"
