According to the official Pure Storage FlashArray//X R2 and R3 hardware documentation, the default factory configuration for a Fibre Channel-enabled FlashArray//XR20 model includes a 2-port 16Gb/32Gb FC Host Bus Adapter (HBA). This card is pre-installed in PCIe slot 2 on each controller. PCIe slot 0 is typically reserved for an optional 2-port Ethernet card used for asynchronous or synchronous replication, not for the primary host connectivity FC card.

A. 2-port in slot 0: This is incorrect because the default placement for the FC HBA is slot 2. Slot 0 is the default location for an optional replication Ethernet card.

C. 4-port in slot 0: This is incorrect due to both the port count and the slot placement. The default configuration uses a 2-port card in slot 2.

D. 4-port in slot 2: This is incorrect because the default factory configuration for an //XR20 model is a 2-port FC card, although 4-port cards are available as an option.

1. Pure Storage, Inc. (2023). FlashArray//X R3 Installation and Upgrade Guide. Section: "PCIe Card Slot Numbering and Default Configurations", Table: "//X10R3, //X20R3, and //C40R3 Default Configurations". This table explicitly lists a "2-port 16Gb/32Gb FC HBA" in "Slot 2" for the //X20R3 model's default FC configuration.

2. Pure Storage, Inc. (2022). FlashArray//X R2 Installation and Upgrade Guide. Section: "PCIe Card Slot Numbering and Default Configurations", Table: "//X10R2 and //X20R2 Default Configurations". This document confirms the same default placement for the R2 generation, specifying a "2-port 16Gb FC HBA" in "Slot 2" for the //X20R2.