Why the value of a is equal to 10?

Question

Even the "a" is not modified why the value is changed.
https://code.sololearn.com/c66s2Mt7he9P/?ref=app

Answer 1

b is an array of 2 elements, but b[3] = 10 changes memory outside of its index range, resulting in undefined behavior. Here, the memory space of b[3] is the same as the variable a.

Answer 2

It was discussed here https://www.sololearn.com/Discuss/1665350/?ref=app

Answer 3

a[3]=10