A. 0.4y = 10/0.4
no, this is clearly the same as above PLUS the /0.4 part
B. 0.4y / 0.4 = 10 / 0.4
yes!
we can divide both sides by the same number
C. 0.4y * 2.5 = 10 * 2.5
yes!
we can multiply both sides by the same number
D. 0.4y / 0.4 = 10 0.4
is there a missing sing here? only if there is a "/" between 10 and 0.4 are those equivalent.