What can be a source of explosions in an auto shop?

The option indicating that all of the listed items can be a source of explosions in an auto shop is correct, as each of these items poses potential hazards that can lead to explosive situations if not handled properly.

Fuel tanks are highly flammable and contain volatile vapors that can ignite in the presence of a spark or open flame. If a fuel tank is damaged or improperly stored, it can lead to a significant risk of explosion.

Car batteries also present a danger, especially if they are overcharged or have damaged cases. They can release hydrogen gas, which is highly flammable. A spark near a battery can ignite this gas, leading to an explosion.

Welding tanks, used for gases like acetylene and oxygen, can also be extremely dangerous. If these tanks are not stored correctly or if there is a leak, they can create an explosive environment. Additionally, if a welding operation produces sparks in the presence of flammable gases, this can result in an explosion as well.

Each of these components has specific safety protocols to mitigate risks, but the nature of these items inherently includes potential explosion hazards, making them collectively dangerous in an auto shop setting.