Which of these sentences uses grammar correctly? whom may i say is calling? who may i say is calling? whose calling?

5. the following question refers to the four selections by albert einstein: these readings show that, between 1939 and 1952, einstein a) abandoned science and turned to political activism. b) revised his opinions about the need for nuclear weapons. c) worked tirelessly to abolish nuclear weapons. d) devoted himself solely to scientific research.