Which amino acid has 2 Asymmetric carbons?

21742832_481655055541428_1138392603696522064_n

21751265_481654925541441_6240810765832443909_n

21728048_481655115541422_4505731027695721582_n

21728484_481655192208081_5330325352646593144_n

21740208_481654742208126_8351716635838096217_n