whichever size fits tightly, probably a metric 15mm
5/8
Take your socket set and try various sockets until you find one that fits...then look at the size on the side of socket...BINGO!!! now you know the size.
42mm is a standard socket. If you mean "what SAE socket fits," none of them do. BTW, what are you trying to get off that's got a nut that big on it?
The part of the tooth that fits into the socket of the jaw(mandible) or maxilla(for upper teeth) is the "root" of the tooth.
Assuming this is a transverse mounted engine the drain plug is located at the rear of the sump 13mm spanner or socket fits the plug.
Fits socket 7 boards.
Socket
Any battery socket that it fits.
Spark plugs use SAE and not Metric. The one that fits it is the one that fits it.
18MM
Don't use a wrench, use a socket. It will be metric, so just try your metric sockets until you find the one that fits.