The old man lives _____ in a ______ house, but he doesn't feel_____.
A:alone, alone, lonely
B:lonely, lonely, alone
C:alone, lonely, lonely
D:alone, lonely, alone
____
某化学兴趣小组的同学对实验室制取CO2及相关性质进行一系列的探究活动.
已知锐角A,B满足2tanA=tanA+B,则tanB的最大值为( )