Which of the following statements about SRAM and DRAM is correct?

Which of the following statements about SRAM and DRAM is correct?

1. a) SRAM consumes less power than DRAM while idle
2. b) SRAM requires fewer transistors per bit than DRAM
3. c) SRAM does not need refreshing while DRAM does
4. d) SRAM stores data in capacitors while DRAM uses flip-flops