ANS:B - invar

The material of construction of surveying metallic tapes is invar. Invar is an alloy of iron (Fe) and nickel (Ni), with a nickel content typically around 36%. It is known for its low coefficient of thermal expansion, which means it does not expand or contract significantly with changes in temperature. This property makes invar particularly suitable for applications where dimensional stability is crucial, such as surveying. Additionally, invar offers sufficient strength for use in surveying tapes while maintaining its dimensional stability over a wide range of temperatures. Therefore, the correct option is: invar