Question

Which of the following could be a nucleotide of RNA?

deoxyribose + phosphate group + thymine

deoxyribose + phosphate group + uracil

ribose + phosphate group + thymine

ribose + phosphate group + uracil

Answer 1

Any ideas?

Answer 2

R +P+u

Answer 3

Here's some differences between DNA and RNA, that can lead you to the right direction.
DNA is a double-standed molecule in the shape of a double helix with interlinking, complementary nitrogenous bases in the form of like a ladder.
The bases that are complementary are adenine and thymine, guanine and cytosine.
It has a sugar phosphate backbone made up of alternating deoxyribose sugars, and phosphates.

RNA is a single stranded molecule, with only has one sequence of nitrogenous bases, (no pairs). It has the same bases except thymine is replaced with uracil, (in the case of mRNA copying the genetic information from DNA). In its backbone it has alternating phosphate but ribo sugars.