What is the possible value of (a + b + c) – 3, if a² +b² +c² = 9 and ab + bc + ca = 8?

Correct option is D

​$$(a+b+c)^2 = 9 + 2 \times 8 \\(a+b+c)^2 = 9 + 16 \\ a+b+c = \sqrt {25} \\ a+b+c = 5 \\ \text{So,} \\ (a+b+c)-3 = 5-3 = 2$$