Because A+3 is the largest

The big side is opposite to the big corner, and the side corresponding to A+3 is the largest. If the corresponding angle is θ, then there must be 90.

Cosine theorem:

cosθ=[a^2+(a+ 1)^2-(a+3)^2]/2a(a+ 1)<； 0

rule

a^2+(a+ 1)^2-(a+3)^2<； 0

a^2-4a-8<； 0

0 & ltA & lt2+2√3

The sum of two sides of a triangle is greater than the third side.

A+A+ 1 & gt； A+3

A & gt2

rule

2 & ltA & lt2+2√3

As long as it is a subset of the above set, it is satisfied.

Only

degree of satisfaction

C