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.

Each type of motor has its particular field of___1___. Because of its simplicity, ___2___ , and durability, the induction motor is ___3___ used for industrial purposes___4___ other types of A.C. motor, especially if a ___5___drive is desired.
If A.C. power is available, all drivers requiring constant speed should ___6___ squirrel-cage induction or synchronous motors because of their ruggedness and lower costs. Drives requiring varying speeds, ___7___ fans, blowers, or pumps, may be driven by wound-rotor induction motors. ___8___, if there are machine tools or other machines requiring adjustable speed or a wide ___9___of speed control, it will probably be desirable to ___10___D.C. motors on such machines and supply them from the A.C. system by motor-generator sets or electronic rectifiers
1.a.usefulness      b.useful      c. use         d. usage  
2.a. economics     b. economical  c.economy     d. economist
3. a. more widely   b.wider       c. more wide   d. widely
4.a. as            b. with       c.than         d. and
5.a. low-speed     b.high-speed   c. fast speed    d. slow-speed
6.a. to use        b. using       c. usage        d.use
7. a. such as      b. such that     c. for example  d. so that  
8.a.Yet          b. However     c. But         d. Although
9.a. range        b. kind         c. kinds       d. ranges
10. a. insert       b. plug        c. install       d. put 
Key:1. a  2.c  3. a  4.c  5.b  6.d  7.a  8.b  9. a  10. c