Although the causes of cancer ________, we do not yet have any practical way to prevent it．

Merry________ as a secretary in the company for five years, but now she is a general manager of the company．

---How can I apply for an online course?
---Just fill out this form and we______ what we can do for you．

---Where were you when I called at your house this morning?
---Oh, I_____ for a friend from Tokyo at the airport．

The manager had fallen asleep where he ______, without undressing．

Bush, before Barack Obama, _______ Brown a similar gift, a leather bomber jacket．

_______ many times, he finally understood it．

--Has your teacher returned from America yet?
--Yes, but he _______ here for only three days before his company sent him to Africa．

Jack’s family _______ their holiday in Shanghai this time next week．

Your cold’s worse, Ann．Go back to bed and I ____ the school to tell them you can’t come．