A:延长线段AB到C,使AB=BC
B:延长射线AB
C:过点A作AB∥CD∥EF
D:作∠AOB的平分线OC
A. spring B. farm the land
C. go on outings D. new green leaves
E. warmer and warmer F. fly kites
G. longer and longer H. four seasons
综合性学习。