Three years ago,a society was set up to________the endangered animals and plants from dying out in this area.
A:obtain
B:preserve
C:observe
D:deserve
①一定有C2H4
②一定有CH4
③一定有C3H8
④一定没有C2H6
⑤可能有C2H2
则上述对该混合烃的判断正确的是( )