According to the passage, deep venous thrombosis usually happens to passengers in ______

A．2) here means__________.A. an enclosed heavily armored combat vehicle that moves on tracksB. a large receptacle for holding waterC. a corporation or group organized for interdisciplinary research in technological or social problemsD. a prison cell or enclosure used for receiving prisoners

A．if a marriage is unhappy, it is likely you will be happier to divorce than if you stay married
B．unhappy couples who stayed married were happier five years later than those who were divorced
C．the "Smart Marriage" conference was sponsored by the Institute for American Values
D．staying married tended to trap unhappy spouses in violent relationships