Hi all. Please help me with this. Imagine I see someone on a street and he says that his son is a marine. Which one of the following sentences is grammatically correct for my response: 1) I didn't know he was a marine. or 2) I didn't know he is a marine. And another scenario: I just saw the news regarding kangaroos and I turn to my friend and say the following sentence. Which one is correct: 1) I didn't know that a kangaroo licked its limb was a sign of stress. (as like in a reported speech) or 2) I didn't know that a kangaroo licked its limb is a sign of stress. (as this is a general behaviour of a kangaroo in distress) Please explain your answer as I am confused. When do <you> use a past tense, was, when someone or something is still happening/existing? How about reported speech where it uses the past tense to report something that is still happening or still as it is? Please explain to me and give me some examples to help me understand this. Thank you very much.