Which of the Following Statements About Nuclear Transport Is TRUE

Which of the following statements about nuclear transport is TRUE?

A) mRNAs and proteins transit the nucleus through different types of nuclear pores.
B) Nuclear import receptors bind to proteins in the cytosol and bring the proteins to the nuclear pores, where the proteins are released from the receptors into the pores for transit into the nucleus.
C) Nuclear pores contain proteins with disordered segments that fill the channel and allow small water-soluble molecules to pass through in a non-selective fashion.
D) Nuclear pores are made up of many copies of a single protein.