Sample GRE question

If all scientists use buffers, and some scientists are LDS, which of the following statements are true?
a) All scientist use LDS Sample Buffer.
b) Some scientists use LDS Sample Buffer.
c) No scientists use LDS Sample Buffer.
d) What, scientists can be LDS?!?

This has been brought to you by the Invitrogen LDS Sample Buffer, the sample buffer specifically made for LDS scientists (especially those that need buffers).