A. has flown
B. is flying
C. has been flying
D. will fly
Past perfect continuous tense is used when a work is being continued for some time from the past. has been flying is the most suitable option.
A. has flown
B. is flying
C. has been flying
D. will fly
Past perfect continuous tense is used when a work is being continued for some time from the past. has been flying is the most suitable option.