Which of the following reagents can be used to convert disulfide bridges into cysteic acid residues?

A) HCO₃H
B) Zn, HCl
C) PhNCS
D) PhCH₂OCOCl
E) CH₃I

The two most abundant isotopes of boron are ¹⁰B and ¹¹B, with ¹¹B being about 4 times more abundant. In the mass spectrum of trimethylborate [(CH₃O) ₃B], ________.

A) the peaks at m/z 103 and m/z 104 have equivalent intensities
B) the peak at m/z 103 has an intensity which is 4 times that of the m/z 104 peak
C) the peak at m/z 103 has an intensity which is 1/4 the intensity of the peak at m/z 104
D) none of the above