Alloy of which metal is used to make aeroplane and parts of the compartment of the train?

Which one of the following metal is NOT an essential component in stainless steel?

Which one of the following alloys contains a non-metal as one of its constituent?

Solder used in soldering metal pieces is an alloy of :

Which of the following alloys has a maximum percentage of Copper?

What are the constituents of alloy solder ?