How is Ran different than Rab and Sar1?
A. Rab and Sar1 are GTPases, and Ran is not
B. Ran does not undergo conformational change, while Rab and Sar1 do
C. Ran is activated by GDP, while Rab and Sar1 is activated by GTP
D. Ran is soluble in both its active and inactive forms, while Rab and Sar1 are membrane-bound in their active forms