Final answer:
The correct answer is option 1, which states that DRAM is slower than SRAM, has a higher packing density, and requires data refreshing.
Step-by-step explanation:
The correct answer is option 1. a, b, and d only. Dynamic RAM (DRAM) is indeed slower than static RAM (SRAM), as it needs to periodically refresh the data it stores, which takes time and slows down access to the stored data. In terms of packing density, DRAM chips have a higher density compared to SRAM, meaning they can store more data in a given physical area.
The need for data refreshing is one of the defining characteristics of DRAM, differentiating it from SRAM, which does not require refreshing. Therefore, statements a, b, and d are correct, while statement c is not, since DRAM is not faster than SRAM.