Decide which of the choices given below would correctly complete the passage if inserted in the corresponding blanks. Mark the correct choice for each blank.

The microwave oven ___1___ in the late___2___  in the US. During World War Ⅱ,microwave technology___3___ a lot in radar equipment, so the technology was advanced. After the war, scientists used the knowledge that they had of microwaves to invent the first microwave oven. In fact, the microwave oven was called a "radar oven” at first ___4___its history. Back then, microwave ovens were ___5___big that only restaurants and other businesses used them.
In the1960s , the first home-use microwave oven___6___ in Japan. In those days, only rich people could___7___ it, but nowadays, microwave ovens are more___8___for people in many countries.
It is easy to heat up yesterday’s leftovers with a microwave oven. As people like you start to understand more about how easy and convenient microwave ovens are, their___9___ grow. Next, let's look at how microwaves___10___ over time.
1.a. was invented  b. invented  c. has invented  d. had invented
2.a.1940s          b.1940’s             c. 2040’s         d 2040s
3.a.used           b.had used           c. was using       d.was used
4 a. because        b. because that        c.because of       d. why
5a. such           b.so                 c. such a         d. very
6 a. was made      b. made              c. is made        d. being made
7a.get            b. to get              c. afford          d. to afford
8a. affordable      b. afford             c. to afford        d. suitable
9a.popularity      b. popular            c. famous         d. well-known
10a. changed      b. have been changed   c have changed     d. changing

Key: 1. a  2. a  3. d 4. c 5.b  6. a 7. c 8.a 9.a 10. a