Which Modification Might Best Produce Cloned Thermostable Enzymes for Industrial

Which modification might best produce cloned thermostable enzymes for industrial applications?

A) increasing the number of cysteine residues in the recombinant protein
B) expression in a eukaryal vector to increase protein methylation
C) expression in a eukaryal vector to increase protein acetylation
D) expression in a bacterial vector to increase protein methylation
E) modifying UGA stop codons to increase peptide length