I think much attention__your pronunciation.a,must be paid to b,ought to be paidto c, may be paid to d,should be paid to, 为什么选a 不选b或d呢?

I think much attention__your pronunciation.a,must be paid to b,ought to be paidto c, may be paid to d,should be paid to, 为什么选a 不选b或d呢?
I think much attention__your pronunciation.
a,must be paid to b,ought to be paidto c, may be paid to d,should be paid to, 为什么选a 不选b或d呢?

I think much attention__your pronunciation.a,must be paid to b,ought to be paidto c, may be paid to d,should be paid to, 为什么选a 不选b或d呢?
must是一定的意思.这里用must是因为much,很多的,大量的,强调了程度.意思是我想你‘必须'花"大量"的时间在你的发音上面.很肯定的口气对不对?语感问题,你多读几遍这个句子就明白了.

因为用must表示推测，I think在这里就是提示你，从句是表示推测得。