In a certain month, the increase in the price of the substitute of X commodity and the increase in the price of the complementary commodity causes the change in the quantity demanded for X commodity respectively to be 50 units and 80 units, then the quantity demanded for X commodity in that month under their joint action ( ).
选项：

A:increases by 30 units;
B:decreases by 30 units;
C:increases by 130 units;
D:decreases by 130 units