MBS, CMO ABS and CDO

CFA Level II
#1

Dear All:

Among these terms, MBS, CMO , ABS and CDO , it seems to me the CDO is the biggest one , I mean it includes everything but ABS ( assets backed-security) can be every already . So Could you please give some explanation about these terms and the level from low to high.

Thank you so much for your time.

Best regards

#2

this question makes no frigging sense.

#3

Why is CDO bigger? They are all 3 letters.