drill [ dril ] (n.) disciplined, repetitious exercise as a means of teaching and perfecting a skill or procedure训练

[例]  easy and short drills

 drive [draIv]1 (n.) energy内驱力,冲劲

[例]  His drive was worn out in the long run.

[同义词]  vigour

2.(v.) urge forward催使，促进

[例]  New technological solutions are needed to tackle the problem and to help drive businesses forward to improve their productivity and output.

[同义词]  propel, push, impel

 due [ dju: ] (adj.) owed应付的，到期的

[例]  This debt became due last week.

 dull [ dQl ] (adj.) (of business or market)sluggish; flat 不景气的

[例] The business of this company is dull this year.

 duplicate [5dju:plikeit ](n) an exact copy of a document such as a letter, a report, a receipt , and invoice etc.副本

[例] Keep the duplicate for your reference.

[同义词] copy

 duty-free (adj.)  exempt from customs duties 免税的

[例]  duty-free merchandise