I'm cold. I __________ my scarf and gloves. [ ]
A. put on
B. take on
C. take off
答案:A
She ______ the national table tennis team in 1988. [ ]
A. joined in
B. joined
C. took part in
D. took part
一根链杆相当于一个约束,而一个单铰相当于()个约束,一个()或()相当于三个约束。