Which of the following is true regarding primes p≡3(mod4)p \equiv 3 \pmod{4}p≡3(mod4)?
They can be written as x2+y2x^2 + y^2x2+y2
They are never congruent to 1(mod4)1 \pmod{4}1(mod4)
The number of such primes is finite
They satisfy p∣n2+1p | n^2 + 1p∣n2+1 for some nnn