Identify the tense used in the following sentence:
They are working on the project together.

In the sentence "They are working on the project together," the tense used is Present Continuous. The words "are working" are in the present participle form (-ing) and are used to form the present continuous tense. The present continuous tense is used to describe actions that are happening at the moment of speaking or actions that are in progress around the current time. In this sentence, the action of "working on the project together" is currently happening, making the correct answer B.