7. The durability of cement concrete is usually improved by
A. increasing the quantity of cement
B. increasing the quantity of coarse sand
C. decreasing the proportion of fine aggregate
D. decreasing the water-cement ratio
7. The durability of cement concrete is usually improved by
A. increasing the quantity of cement
B. increasing the quantity of coarse sand
C. decreasing the proportion of fine aggregate
D. decreasing the water-cement ratio