What is NOT a Characteristic of Radiolarians

Question

What is NOT a characteristic of radiolarians?  
A) They have perforated shells of calcium carbonate.
B) They form part of the plankton.
C) They have two cytoplasmic layers.
D) They have vacuoles that impart buoyancy.
E) They are heterotrophic protists.

Accepted Answer

Radiolarians have shells made of silica, not calcium carbonate. Calcium carbonate shells are characteristic of other marine organisms, such as foraminifera, not radiolarians.