The side group of lysine is protected by which of the following protecting groups?

• A. A tertiary butyl group (tBu)
• B. A triphenylmethyl group (Trt)
• C. 2,2,5,7,8-pentamethylchroman-6-sulphonyl group (PMC)
• D. A tertiarybutyloxycarbonyl (tBOC)