If is the Coefficient of linear expansion of block and L denotes length, T denotes Temperature then which one of these is true (A)

If α is the Coefficient of linear expansion of block and L denotes length, T denotes Temperature then which one of these is true
(A) dL - α L dT = 0
(B) dL + αL dT = 0
(C) αdL - L dT = 0
(D) αdL - +L dT = 0