Read the sentence and answer the question. since the late 1970s, many astronauts have held advanced degrees this education has been useful for mission specialists. which correctly shows where a semicolon is needed in the sentence? a. since the late 1970s, many astronauts have held advanced degrees; this education has been useful for mission specialists. b. since the late 1970s, many astronauts have; held advanced degrees this education has been useful for mission specialists. c. since the late 1970s, many astronauts have held advanced degrees this education has been useful; for mission specialists. d. since the late 1970s; many astronauts have held advanced degrees this education has been useful for mission specialists.