Answers: A and C – Since you are installing 64bit version of Windows 8.1, you need to have at least 2Gb of RAM and 20 GB of Hard disk space.
At the minimum, your system should have the following specs:
Processor: 1 GHz or faster with support for PAE, NX, and SSE2
RAM: 1 GB (32-bit) or 2 GB (64-bit)
Hard disk space: 16 GB (32-bit) or 20 GB (64-bit)
Graphics card: Microsoft DirectX 9 graphics device with WDDM driver