It is that he has been addicted to the drugs and has difficulty quitting it.
A. obviously
B. apparently
C. possibly
D. likely
网友回答
A. obviously
B. apparently
C. possibly
(答案→)D. likely
解析：考查句型：It is likely that 很可能…，likely 形容词，可能的，A、B、C为副词，意思分别为显然地、明显地、可能地。此题应用形容词，所以选D。