С. надо раскрыть скобки и поставить глагол в present perfect. вот предложения: 1) our son (learn) how to reed. 2) scientists (split) the atom. 3) english (become) one of the most popular courses at the university. 4) i think i (see) that movie before. 5) joan (learn) two foreign languages. 6) you (see) that movie? - i (see) that movie twenty times. 7) people (travel) to the moon. 8) james (not finish) his homework yet. 9) the rain (not stop). 10) she (be) in england for six months.

Our son has learned how to read. Scientists  have  split  the atom. English has become one of the most popular courses at the university. I think I have seen that movie before. Joan has learned  two foreign languages.  Have you seen that movie? – I have seen that movie twenty times. People have travelled to the moon. James has not finished his homework yet. The rain has stopped. She has been in England for six months.            Present Perfect       has / have  + Past participle       ( to see-saw- seen)