In what way are all living organisms on earth similar?

The correct answer is C. all use a code with the same five kinds of nucleotide.

Explanation:

All the organisms on the planet use the same genetic code with the same nucleotide sequence for the incorporation of the same amino acids into the protein. Therefore genetic code is universal among all the organisms whether they are plants, animals or microbes.

This genetic code is made up of three nucleotides in every individual out of five kinds of nucleotides present in the organisms and these three nucleotides are called triplet codon.  

Triplet codons code for a particular amino acid and these triplet codons are the same in all organisms for a particular amino acid.  

Therefore, the right answer is C. all use a code with the same five kinds of nucleotide.

ya the other dude is right