What is a convertible security?

multiple choices are:

it allows the holder to put the top down

it allows the holder to convert it into shares of common stock

options and futures are each traded in convertible form

bonds and preferred stock are each traded in convertible form

A and B

A and C

A and D

B and C

B and D

C and D

all but A

all but B

all but C

all but D

all are true