Giúp e với Exercise 3: Choose the best answer . 1. As there was no transport of any kind , he had to make the journey foot . . A. by B. at C. on D. with 2. Dentists recommend brushing teeth with a fluoride toothpaste to them from decay . A defend B. protect C. aim D. guard 3. My older brother has recently —_golf to provide himself with some relaxation . A. take on B. take over C. take with D. take up 4. The management has authorized wage increase for all A. employees B. employers C. citizens D. residents 5. These measures have been taken with a to increase the company's profits . A. view B. purpose C. goal D. reason 6. We both an attempt to be friendly despite recent arguments . A made B. took C. did D. led 7. I'm feeling a bit the weather , I think I'm getting a cold . A. with B. for C. upon D. under 8. Daisy : “What a lovely house you have ! " I love Ms. Le - Mary : " . A. Lovely , I think so . B. Thank you. Hope you will drop in . C. Of course . It's not expensive . D. No problem . 9. These seats are for special guests . Gentle Ms. Le A. preserved B. reserved C. retained D. sustained 10. We regret to inform you that the materials you ordered are A. out of work B. out of stock C. out of reach D. out of practice 11 As a student , he took an evening job to keep the from the door . A. wolf B. dog D. bear C. pig

Con lắc lò xo dao động điều hoà , khi giảm khối lượng của vật lên 4 lần thì tần số góc dao động của vật: A. tăng lên 4 lần . B. giảm đi 4 lần . C. tăng lên 2 lần . D. giảm đi 2 lần .