The retired professor, _____ in his new
问题:
The retired professor, _____ in his new book in the past three years, hasn’t realized the decline in his health.
A.involved
B.being involved
C.having involved
D.to be involved
The retired professor, _____ in his new book in the past three years, hasn’t realized the decline in his health.
A.involved
B.being involved
C.having involved
D.to be involved