2.28. A. caught B. knew C. met D. became

A. 　植物进化与维管束

B. 　植物桥梁:维管束

C. 　维管束与植物生长

D. 　植物的面包:维管束

A. 　you needn’ t

B. 　you won’ t

C. 　you can’t

D. 　you don’ t

D. 　 is arriving

A. 　 broke

B. 　 started

C. 　 declared

D. 　 spread

A. 　 wealth

B. 　 knowledge

C. 　 courage

D. 　 strength

A. 　 though

B. 　 since

C. 　 but

D. 　 if

A. 　 so

B. 　 or

C. 　 but

D. 　 for

A. 　 married

B. 　 separated

C. 　 accepted

D. 　 united