—Look! He’s running so fast!
—Hard to______ his legs were once broken.
| A．know | B．imagine | C．realize | D．find |
They form a polar molecule, ____ is, ____ with a slightly positive end and a slightly negative end.
| A．which; that | B．it; one | C．that; one | D．one; that |
They find themselves surrounded by colorful rocks, fishes, seashells and plants, all ____ slowly in the blue water.
| A．waving and moving | B．waved and moved |
| C．waved and moving | D．waving and moved |
Even though the pure water is ____ gives sea water its main properties, the salinity of sea water affects both its weight and freezing point.
| A．the one | B．which | C．what | D．that |
Mike is Mrs.’ pet student, ____ all her students no one else is as nice as he.
| A．because | B．because of | C．with | D．as |
He came running along and climbed ____ the train just as it was about to leave.
| A．aboard | B．board | C．abroad | D．on abroad |