Me plzz all for my points read the sentence and answer the question.

in 1978, nasa changed the organization of the astronauts 20 mission specialists and 15 new pilot astronauts were chosen.

which correctly shows where a semicolon is needed in the sentence?

a.
in 1978, nasa changed the organization of the astronauts 20 mission specialists and 15; new pilot astronauts were chosen.

b.
in 1978, nasa changed the organization of the astronauts; 20 mission specialists and 15 new pilot astronauts were chosen.

c.
in 1978, nasa changed the organization of the astronauts 20 mission specialists; and 15 new pilot astronauts were chosen.

d.
in 1978, nasa changed the organization of the astronauts 20 mission specialists and 15 new pilot astronauts; were chosen.