Which of the following expansion slots is 64-bit?

Pci x is 64bits also just its parallel not serial so is it A or B

PCIe is wrong, it’s a 10bit bus using 10. PCIe 1.x uses an 8b/10b encoding scheme that results in a 20 percent ((10-8)/10) overhead on the raw bit rate, therefore delivering an effective 250 MB/s max data rate.