A is a infinitive, so we can take that out. B is past, and D is future tense.
The answer would be C because rises is the correct from of present.
A progressive form of a verb is formed with the ending "-in": the only verb form in the options that is formed with the ending "ing" is in option b.
The correct option is b: will have been falling. This tense is the future perfect progressive tense.
