Which one of these, is the most ductile metal?
(A) Al
(B) Au
(C) Cu
(D) Ag

Hint: It has the highest corrosion resistance of all the metals and it is corroded only by a mixture of nitric and hydrochloric acid. It is a noble metal because it does not oxidize.

Complete step by step answer:
> First , let us understand the meaning of ductility.
Ductility is the physical property of a material associated with the ability to be hammered thin or stretched into wire without breaking.
Now, let us see why gold is the most ductile metal?
> Gold is the most malleable and ductile metal, 1 ounce i.e, 28g of gold can be beaten out to 300 square feet. It is a soft metal and is usually alloyed to give it more strength. It is a good conductor of heat and electricity, and is unaffected by air and most of the reagents.
Gold is metallic, with yellow colour in solid , but when finely divided it tends to be in black colour.
> Let us see few applications of gold
Gold is used in jewellery, glass and electronics. Jewellery consumes around 75% of all gold produced. Gold electroplating is used in the electronic industry to improve their solderability and to protect their copper components.
Hence, Au is the most ductile metal. So, option B is the required answer.

Note: Gold appears yellow because it absorbs blue light more than it absorbs other visible wavelengths of light; the reflected light reaching the eye is therefore lacking in blue compared to the incident light. Therefore,it appears yellow to human eyes.