5. 若有兩個彼此獨立的隨機變數 x 以及 y,以下何者為真?(此題僅需選出正確選項)(10%)(A) \( E[x + y] = E[x] + E[y] \)(B) \( E[(x - y)^2] = E[x^2] + E[y^2] \)(C) \( E[xy] = 0 \)(D) \( E[xy] = E[x]E[y] \)