a. 艰苦的, 费劲的, 勤劳的

◆记忆方法一：
词根词缀记忆法：laborious a 辛苦的，吃力的（labor+ious→劳动的→辛苦的）,labor=labor,表示“劳动”

neighbor/neighborhood/labor/laborer/laborious/hard-working/diligent
记忆：
1. neighbor [ 5neibE ] n. 邻居, 邻国 We should get on well with our neighbors.我们应该与邻居好好相处。
2. neighborhood [ 5neibEhud] n. 附近, 邻近 Good neighborhood is more helpful than our relatives far away. 远亲不如近邻。
3. labor [ 5leibE ] la-bor la, 音“累”，劳累 n. 劳动 vi. 劳动 The labor of the cleaners should be valued.清洁工人的劳动应该受到尊重。
4. laborer [ 5leibEriN ] n. 劳动者（尤指体力劳动者） There is no wealth without laborers.没有劳动者就没有财富。
5. labor force n. 劳动力 In some way our labor force is rather cheap.从某个角度上说，我们的劳动力太便宜了。
6. laborious [ lE5bC:riEs ] 　adj. (指工作)艰苦的, 费力的, (指人)勤劳的 The Chinese is a laborious people .中国人是一个勤劳的民族。
7. hard-working　adj. 勤劳的，勤奋的 Jack is not a bit hard-working.杰克根本不是勤奋的人。
8. diligent [ 5dilidVEnt ] dili-gent, 音“地理尽”知的，只有用功才能做到，adj.勤勉的, 用功的, 细心而继续不断的 Though he's not clever he's diligent and has often done well in the examinations.虽然他并不聪明，但他很勤奋，他考试经常都考得好。
另类阅读：
We are hard-working laborers who earn their lives by honest labor. We are ready to do any laborious job.
Our neighbor is laboring hard in his garden in the neighborhood.