Fill in the blank with the most appropriate word. It is highly probable that more and more solar energy ________ in the future.

The correct answer is: will be used.

The verb “will be used” is the most appropriate word to fill in the blank because it is the only option that is in the future tense. The other options are in the present tense, which is not grammatically correct in this context.

The sentence is about the future, so it makes sense to use a future tense verb. The verb “will be used” is also the most common way to express probability in English.

Here are some other examples of how to use the verb “will be used”:

• It is highly probable that more and more solar energy will be used in the future.
• The new technology is likely to be used in many different industries.
• It is certain that the new law will be used to prosecute criminals.

I hope this helps!