Which triplet codon acts as a stop signal for the process of translation?

$A$ triplet codon means

The genetic code was deciphered by chemical synthesis of trinucleotides by:

The sequence is $AGC \, ACA \, UUU \, AUG \, CCG \, AGC$. Which of the following options will not change the reading frame?

Which code is present in the $DNA$ molecule to produce the necessary chemicals as per the parental instructions?

Which of the following $m-RNA$ sequences can be completely translated into a polypeptide chain?
$(a)\ 5'-AUG\ UGA\ UUA\ AAG\ AAA-3'$
$(b)\ 5'-AUG\ AUA\ UUG\ CCC\ UGA-3'$
$(c)\ 5'-AGU\ UCC\ AGA\ CUC\ UAA-3'$
$(d)\ 5'-AUG\ UAC\ AGU\ AAC\ UAG-3'$