Помогите пожалуйста! Задание: Put the verbs in brackets into the "Past Simple" or the "Present Perfect"

2) it has existed   3) has developed  4) found   5)  explored  6) saw   7) stopped   8) caught   9) I always wanted    10) but I didn't think   11) have studied  12) he said   13 ) has bought    14) They showed