13. experience (n.) 经历，经验 / (v.) 经历　 expensive (adj.)=dear / cheap　 experiment (实验)

12. shop assistant

11. tie ---- tying / tied / tied　　 lie ----lying / lay / lain　　 die---dying / died / died

10. certainly / of course / sure

9. discuss (v.) 讨论---- discussion (n.)

make a contribution to doing sth. 为…做贡献

make a decision to do sth. 决定做…

8. mean (meant/ meant) ---- meaning (n.)---- meaningful / meaningless

7. delight(n.) ---- delightful　 /　 joy ---joyful

6. help ---- helpful ---- helpless

5. shine ---- shiny

4. perform ----performance(s) ---- performer (n.)