I want to know ----- about him

答案：C
a lot of = lots of 后接可数名词的复数,或者不可数名词,而后面是介词about,所以AB排除,many表示“许多的,大量的”,后接复数名词,也排除.a lot是副词,表示“很,非常,常常”,在句中修饰动词know,所以是正确答案.