请问condition和conditions在用法上有什么区别?再加一道语法题

请问condition和conditions在用法上有什么区别？

还有这道题

With the rapid increase of crimes concerning credit card, people have begun to look at the use of credit card ______.

A. the other way

B. another way

C. by the other way

D. by another way

答案选B

请问in是可以省略还是这本来就是一种固定用法？