______ the Atlantic Ocean crosses the equator, the trade winds cause a flow of water to the west．
| A．That | B．When | C．Where | D．Though |
Unfortunately, when I dropped in, Dr. Green ______, so we only had time for a few words.
| A．just left | B．has just left | C．had just left | D．was just leaving |
The animal makes a strange sound, slightly ______ the bark of a dog.
| A．resembling | B．requesting | C．resisting | D．reflecting |
You got back so late and you didn’t even give me a proper reason _______ you hadn’t called me! I’m very unhappy with you.
| A．when | B．why | C．how | D．which |
There was a big dog ______ in front of Mr. Hill’s house, so David didn’t dare to go near it.
| A．to sit | B．sat | C．sitting | D．sits |
The tourists can not help wondering ______ the ancient people could manage to complete the magnificent building without modern equipment.
| A．that | B．how | C．where | D．what |