Question

急！一道英语选择题,请详细解释

7.______they wanted to go out, they could always count on me to stay with the baby.
A.unless B,if C.on condition that D.Given that
麻烦翻译，其中C on condition that英汉词典解释“如果，在******的条件下”也就是说和B.if 有相同的意思，但为什么不选C，C和B有什么本质区别

Answer 1

最大区别，是if常用于主观方面的条件，这里they wanted，显然是主观方面的条件；on condition that 则侧重于客观方面的条件，与 in case that 近似。 再如：If you want to go ，you can now。显然这句的if也不能用on condition that代替。

Answer 2

楼主可以看看一下四个例句：
1. I will go abroad on condition that my husband goes with me.
如果我丈夫能和我一起去, 我就出国。

2. I'll come on condition that John is invited too.
如果约翰也受到邀请，我就来。

3. Medieval system, where land was grant by a king to his aristocracy, and by the aristocrat to the peasant, on condition that each pay a service( or feudal duty) to his superior.
一种中世纪的制度：国王将土地转让给贵族，贵族再转让给农民。条件是每个人必须向他上级服役或交税。

4. The juvenile offender was released from custody on condition that he should find a job immediately and stay out of trouble for six months.
那个年轻的罪犯已从拘留所释放，条件是：他应该马上打一份工作，六个月内不得惹事生非。

从中可以看出，on condition that只是用在句中，而不能用在句首，至少应该说是很少用于句首。这个就是根本的区别。

Answer 3

意思相近
但用法不同的吧
觉得C不能用在句首

Answer 4

C在具体情况下，B有一种假设，或虚拟

Answer 5

B