Which of the following elements are good insulators?
li and ca
ag and au
p and s
th and u

P and S

Explanation:

Phosphorus (P) and sulfur (S) both are non-metals. Non-metals are good insulators i.e. they do not let electricity/current pass through them. The reason why non-metals are insulators is because they do not have free electrons in contrast to metals which have free electrons because of which they are good conductors of electricity.

Metals like Li (lithium), Ca (calcium), Ag (silver) and Au (gold) are conductors not insulators. Uranium (U) and thorium (Th) are radioactive but still they are metallic elements so they are not insulators.  

So only option 3rd is right.

not the best question format lol but what i think might as scale color is controlled by a single gene with two alleles, the green allele and the yellow allele. when moths that are homozygous for green scales are mated with moths that are homozygous for yellow scales, 100% of the offspring have green scales.