单项选择题
"Do you hear someone knocking at the door" "Yes, I did. I heard him () three times."
A．knocking B．knocked C．being knocking D．knock
单项选择题 The two thieves fled the town separately, () a bag.
单项选择题 A burning cigarette he threw into the wastepaper basket () fire to the hotel.
单项选择题 If a baby bird stays () for two or three weeks after leaving the nest, it has a fair chance of becoming an adult.
