What is a benefit of PCIe version 3.0 over PCIe 2.0?

A.
It supports InfiniBand in full throughput mode.

B.
It reduces the profile of the option cards.

C.
It decreases the base clock speed to save power.

D.
It doubles the total bandwidth on the bus.

Explanation:
PCI Express 3.0 upgrades the encoding scheme to 128b/130b from the previous 8b/10b encoding, reducing the
bandwidth overhead from 20% of PCI Express 2.0 to approximately 1.54% (= 2/130). PCI Express 3.0’s 8 GT/s
bit rate effectively delivers 985 MB/s per lane, practically doubling the lane bandwidth relative to PCI Express
2.0.
https://en.wikipedia.org/wiki/PCI_Express#PCI_Express_3.0