After R2 is stationary inside the ISS, it will. A get more parts, become mobile, and go outside.

B help engineers develop better future robonauts.

С be assigned specific jobs inside the ISS.

D return to a space center in Arizona for more tests.​

the answer is:

when will (v) the books (n) be (v) due?

nouns refer to people (other than pronouns), places and things, whereas verbs describe actions and are usually part of the predicate of a sentence. finally, pronouns can work as nouns and identify the participants in speech.

in the example sentence, "will" is a verb part or auxiliary verb, "be" is an infinitive verb and "books" is a plural noun.

i think continuous as the stars that shine and twinkle on the milky way, they

stretched in never-ending line along the margin of a bay; ten thousand saw

i at glance, tossing their heads in sprightly dance.

1.c

2.b

3.c

4.b

5.c

6.c

7.d

8.b

9.b

10.d

11.c

12.d

13.b

14.d

15.b

16.a

17.c

18.b

19.d

20.b

21.a

22.b

23.c

24.b

25.c

26.d

27.c

28.d

29.d

30.a

31.c

32.b

33.a

34.d

35.c

36.a

37.b

38.a

39.d

40.c

41.e

42.a

43.c

44.b

45.d

46.b

47.e

48.c

49.d

50.a

51.b

52.a

53.d

54.c