Заполните пропуски глаголами to think и to know. We...we...the answer You...you...the answer He...he...the answer She...she...

We think we know the answer.You think you know the answer. He thinks he knows the answer. She thinks she knows the answer. They think they know the answer.There is no comma in such cases. You can put \'that\' in the sentence. For example: We think that we know the answer.