Which of the following sentences are statements? (a) 32 C 42 D 52. (b) a2 C b2 D c2. (c) There exist integers a, b, and c such that a2 D b2 C c2. (d) If x2 D 4, then x D 2. (e) For each real number x, if x2 D 4, then x D 2. (f) For each real number t , sin2 t C cos2 t D 1. (g) sin x < sin 4 . (h) If n is a prime number, then n2 has three positive factors. (i) 1 C tan2 D sec2 . (j) Every rectangle is a parallelogram. (k) Every even natural number greater than or equal to 4 is the sum of two prime numbers