英语单选疑问This method creats an atmosphere_____to expansiona.pre

英语单选疑问
This method creats an atmosphere_____to expansion
a.preferable b.profitable c.favorable d.superior
Disagreements among engineers were_____to the plan
a.vital b.fatal c.crucial d.critical
Living in the central Australian desert has its problems,_____obtaining water is not the least.
a.for which b.to which c.of which d.in which
答案我全知道,在这里提问是想知道为什么这么选
希望高手赐教