a. 有帮助的, 有益的, 有用的

◆记忆方法一：
联想方式：help（v.帮助）；ful（形容词后缀）
help（v.帮助）的形容词形式helpful（有帮助的）。
◆记忆方法二：
联想方式：help（v.帮助）；ful（形容词后缀）
记忆方法：help（v.帮助）的形容词形式helpful（有帮助的）。

favor/favorite/favorable/unfavorable/help/helpful/helpless/aid/AIDS/first/aid/assist/assistant/assistance
记忆：
1. favor [ 5feivE ] n. 好感, 宠爱, 好意 Could I ask for your favour?能不能请你帮个忙？
2. favorite [ 5feivErit ] n. 特别喜欢的人(或物), 心腹 adj. 喜爱的, 宠爱的, 中意的 Everyone has his favorite. But it’s wrong to force others to love your favorite.每个人都有自己的最爱。但强迫他人喜欢你的最爱的做法却是不对的。
3. favorable [ 5feiErEbl ] adj. 赞成的, 有利的 Now the international situation is favorable to develop our economy. 现在国际形势对发展我们的经济有利。
4. unfavorable [ 5Qn5feivErEbl ] adj. 不利的 What Chen Shubian does is unfavorable for the stability across the straits.陈水扁的所作所为对海峡两岸的稳定不利。
5. help [ help ] n. 帮忙, 补救办法, 助手 v. 帮助, 有助于 Without your help, I would have failed the exam again.没有你的帮助，我这次考试又会不及格。 help sb help sb with sth help sb (to) do sth help oneself to sth 自便用，自便吃
6. helpful [ 5helpful ] adj. 有帮助的, 有益的 An English dictionary is helpful in our study. 一本英语词典在我们的学习中有用。
7. helpless [ 5helplis ] adj. 无助的, 没用的 Regretting is helpless. Why not learn a lesson and do better from now on?后悔是没有用的。干吗不吸取教训，从现在起做得更好些呢？
8. aid [ eid ] n. 帮助, 援助, 帮助者 vt. 资助, 援助, 帮助 First aid should be given to the wound without delay.应该马上给伤者急救。 first aid n.(对伤患者的)急救
9. AIDS [eIdz] 艾滋病 So far no effective medicine has been found to cure AIDS.到目前为止还没有治好爱滋病的有效药物。
10. assist [ E5sist] 词根sist含义为stand站；assist, 站在一旁 n. 援助, 帮助 Mary assists the professor with the important experiment.玛丽协助教授做重要的实验。
11. assistant [ E`sIstEnt ] n. 助手, 助教 adj. 辅助的, 助理的 The expert need an assistant. Do you have interest?那名专家需要一个助手，你感兴趣吗？
12. assistance [ E5sistEns ] n. 协助, 援助, 补助 The smooth work was due to his effective assistance.他有效的帮助使工作很顺利。
另类阅读：
Don’t feel helpless in an unfavorable situation. Even if your favorite friend doesn’t do you a favor, I may be of some help. I can offer you some aid or assistance even when AIDS hits you. .
2. feel feeling feet(foot) feed(food) fell