Finding maximum duration

CFA Level I
#1

Which bond (of same maturity) will have maximum duration:
ZCB
Perpetual
Plain Vanilla

Can you please let me know how to logically proceed to answer the above question and then provide answer explanation?

Thanks

#2

Depends on the specific characteristics.

Do you have more details?

#3

ZCB is provided as answer.

I do not have any more details

#4

Did you add the “of same maturity”, or did I simply miss that before?

In any case, it doesn’t make sense: the perpetual bond doesn’t have a maturity.

The point they’re trying to make, I suspect, is that the larger the coupon payment, the shorter the duration.

#5

The words " of same maturity" was in the question always.

I did not add or make any changes to question.

Thanks for your inputs