【正确答案】 B

【答案解析】[理由] 本句测试下列固定结构：
It is/was+时间副词/介词短语/副词从句+that引导的名词从句 直到……才……
时间副词：then(那时)、yesterday(昨天)、next year(明年)
介词短语：by bus(搭公车)、by train(乘火车)、by plane(乘飞机)、with sb's help(有某人的帮助)
副词从句：not until…(直到……才)、only when…(只有当……才)
[例] It was then that I found I had lost my wallet.
(直到那时我才发现我弄丢了皮夹。)
It was yesterday that I met him
(我是昨天遇见他的。)
I was by bus that I came here.
(我是乘公交车来这儿的。)
I was with your help that I succeeded.
(我成功是因为有你的帮助。)
It was not until he left that I arrived.
(直到他离开了我才到。)
根据上述，原句起首有it was，之后有not until引导的从句，得知空格内应置that引导的名词从句，故(B)应为正选。