Base-pair substitutions involving the third base of a codon are unlikely to result in an error in the polypeptide. This is because\
a. base-pair substituions are restriced to introns, and theseregions are later deleted from the mRNA.
b. a signal-recognition particle corrects coding errors beforethe mRNA reaches the ribosome.
c. base-pair substitutions are corrected before transcriptionbegins
d. transcribed errors attract snRNPs, which them stimulatesplicing and correction.
e. most tRNAs bind tightly to a codon with only the firstbases of the anticodon.