The conditional operator (?:) ________. A: is the only ternary operator in C B: is a unary operator C: associates from left to right D: accepts two operands

5-1.In the ternary system CaO-Al2O3-SiO2,<br/>there are 8 eutectic points, 7 double-peritectic<br/>points and 9 saddle point. According to phase rule, at most, it can<br/>be divided into ____sub-triangles A: 8个 B: 7个 C: 9个 D: 15个