Which of the following are two de-soldering methods?

The two de-soldering methods that are widely recognized are 'sniffing' and 'wicking'.

Wicking refers to the use of a desoldering braid, which is a copper braid that absorbs molten solder when heated. When the braid is placed over the soldered joint and heated with a soldering iron, the solder is drawn into the braid, effectively removing it from the connection. This method is especially useful for fine-pitched components or areas where there is a need to remove solder without applying excessive heat, which could damage surrounding components.

Sniffing, in this context, is a less formal term that may be interpreted as the technique of using a vacuum desoldering tool or similar device to "sniff" or suck away the molten solder. This method allows for precise removal of solder by creating a suction effect that pulls the solder away from the joint, making it easier to remove components without damaging the board.

The other options do not accurately describe methods used for de-soldering. Heating and cooling refer to temperature changes but do not describe specific techniques for solder removal. Cutting and grinding involve physically altering components or the PCB, which is not a preferred method for desoldering. Slicing and unscrewing do not