Genetic Code

Salient features of the genetic code: the codon is a triplet; one codon codes for only one amino acid, so the code is unambiguous and specific; some amino acids are coded by more than one codon, so the code is degenerate; it is read in a contiguous fashion without punctuation; and it is nearly universal.
'Ambiguous' would mean that one codon codes for more than one amino acid, which is not the case.
Hence being ambiguous is not a salient feature of the genetic code.

Salient features of the genetic code: the codon is a triplet; one codon codes for only one amino acid, so the code is unambiguous and specific; some amino acids are coded by more than one codon, so the code is degenerate; the code is nearly universal.
The codon is read in mRNA in a contiguous fashion; there are no punctuations (commas) between codons.
So the statement that a codon is read in a non-contiguous fashion is not true.
Hence the answer is 'A codon in mRNA is read in a non-contiguous fashion'.

George Gamow had proposed that the code should be a triplet, since 4 bases must code for 20 amino acids ($4^3 = 64$).
Marshall Nirenberg's cell-free system for protein synthesis finally helped the code to be deciphered: Nirenberg and Matthaei used a synthetic poly-U mRNA and obtained a polypeptide of phenylalanine, showing that UUU codes for phenylalanine.
This work established experimentally that the code is a triplet.
Beadle and Tatum proposed the one gene–one enzyme hypothesis; Hershey and Chase proved that DNA is the genetic material; Morgan and Sturtevant worked on linkage and gene mapping.
Hence the answer is Nirenberg and Matthaei.

Out of 64 codons, 61 code for amino acids and 3 do not code for any amino acid; these three are the stop (terminator) codons: UAA, UAG and UGA.
So UAG and UGA are both stop codons, and this pair is correctly matched.
AUG codes for methionine and also acts as the start codon, but ACG codes for threonine.
UUA codes for leucine, but UCA codes for serine.
GCU codes for alanine, but GUU codes for valine.
In each of the other pairs only one codon matches the function given, so the correct pair is UAG, UGA - Stop.

Four bases taken three at a time give $4^3 = 64$ codons.
Three of these, UAA, UAG and UGA, are stop (nonsense) codons that do not code for any amino acid.
The remaining $64 - 3 = 61$ codons (sense codons) code for the 20 amino acids. Since there are more codons than amino acids, most amino acids have more than one codon (degeneracy).
AUG codes for methionine and also acts as the start codon.
So 61 codons code for all 20 amino acids.

UCG codes for serine. The start codon is AUG (methionine). So 'UCG – start' is wrong.
UUU codes for phenylalanine (the first codon deciphered by Nirenberg). The stop codons are UAA, UAG and UGA. So 'UUU – stop' is wrong.
UGU codes for cysteine. Leucine is coded by UUA, UUG and CUU, CUC, CUA, CUG. So 'UGU – leucine' is wrong.
UAC (and UAU) codes for tyrosine. Correctly matched.
So the correct match is UAC – tyrosine.

There are 61 sense codons but only 20 amino acids, so most amino acids are coded by more than one codon (e.g. leucine has 6 codons, glycine has 4).
This property, where one amino acid is specified by more than one codon, is called degeneracy (redundancy) of the genetic code.
Wobble explains how one tRNA can read several of these codons; universality means the same code is used in almost all organisms.
So this is called degeneracy of the genetic code.

AUG is the initiation (start) codon. It codes for methionine (formylmethionine in bacteria) and marks the start of translation.
UAG is a stop codon; AUC codes for isoleucine and CCU for proline.
So the initiation codon is AUG.