we are now living in ____ world,where computers rule our work and daily life.So online searches have became ____ must.

we are now living in ____ world,where computers rule our work and daily life.So online searches have became ____ must.
A、a; a B、a; the C、the; a D、the; /
主要是第一个空,为什么.
后一个空是 a
a must 必须的条件，不可缺少的东西
答案选A…………