D
设甲单侧面积是a,乙为b,丙为c,底面积为s.
则a+b+c=s,
(2a+s):(2b+s):(2c+s)=2:3:4,
2a+s+2c+s=2(2b+s),推出a+c=2b,
4(2b+s)=3(2c+s),
8b+4s=6c+3s,
8b换成4a+4c得出:
4a+4c+4s=6c+3s,
化简s=2c-4a,
2s=4c-8a,
2s=2a+2b+2c,
2s=3a+3c.
2b换成a+c,
3a+3c=4c-8a,
得出c=11a,
a:c=1:11,
a:b:c=1:6:11.
故选D.