Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions. As soon as the spacecraft _______

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.
As soon as the spacecraft ___________ into space, the crew started to observe the sun.

A.
was travelling
B.
has travelled
C.
had travelled
D.
travelled