What are the complementary mrna and trna sequences for this sequence of dna bases: cga?

The sequence on mRNA will be  GCT 

This follows base pairing rules were G always pairs with C and A  always pairs with T

tRNA however does not have a complementary sequence for DNA sequence because the  function of tRNA  is to translate the information that has been copied (transcribed) on mRNA from DNA and determine which amino acid corresponds to that information.

Once information from DNA has been transcribed on mRNA in the nucleus of the cell, mRNA leaves the nucleus and enters the cytoplasm where it attaches to a ribosome.   tRNA then comes and begins to read the information on the attached mRNA but it only reads it in triplets that is a set of three nucleotides e.g. ATG or CGA but not single nucleotides.  This is because the code for each amino acid is in triplets, called codons, and not single bases or nucleotides.

Therefore in our case the codon GCT codes for the amino acid Alanine so tRNA will read this codon on the mRNA and fetch Alanine from the amino acid pool in the cytoplasm,then bring it to the ribosome where it will be linked with other amino acids to make a specific protein.

do yall know the answer?

gold i'm pretty sure i might be wrong