Complete this sentence. if volume remains the same while the mass of a substance the density of the substance

increases, stay the same
decreases, stay the same
decreases, increase
increases, increase

 increases, increase

Density of a substance is calculated by mass/volume formula. In this case, if the mass of the substance changed then the density must be changed too so option A and B are out.
If the volume is same but mass increased, then the density will increase, or vice versa. Then the possible answer increases, increase or decrease, decrease

Cin carbonh in hydrogeno in oxygen