How did you know which tRNA molecule would attach to the mRNA strand

Matching of base pair is the reason for the tRNA molecule attachment to the mRNA molecule.

Explanation:

The mRNA strand is the process of synthesizing, making proteins from amino acids. tRNA molecules bring the amino acids to the mRNA strand. The tRNA molecule that will attach to the mRNA strand. The pairing of base pairs takes place as Cytosine (C) with guanine (G), and adenine (A)  with uracil (U).The molecules of tRNA match up with the amino acids then the tRNA molecules which carry their amino acids towards the mRNA strand by pairing is called translation. The pairing of the is done by the anticodon in which the tRNA matches up with a codon on the mRNA to get the desired base pair.  

The answer is letter c