1. The problem asks to determine whether each sentence is a proposition or not. 2. A proposition is a declarative sentence that is either true or false, but not both. 3. Let's analyze each sentence: a) Every integer is a real number. — This is a proposition because it is a declarative statement that is true. b) x + y is a real number. — Not a proposition because it contains variables without specified values. c) $x^2 \geq 0$ for all real numbers $x$. — This is a proposition and it is true. d) Thank you for your cooperation! — Not a proposition; it's a command or expression. e) The first human being lived in Africa. — Proposition; it is declarative and can be true or false. f) I am determined to score A in Math 1011. — Not a proposition; it's a personal statement. g) The sum of two odd numbers is even. — Proposition; true statement. h) Bahir Dar is a city in Ethiopia. — Proposition; true. i) 9 is a prime number. — Proposition; false. j) Bring me a glass of water. — Not a proposition; it's a command. k) 5 + 6 = 12 — Proposition; false. Final answers: - Propositions: a, c, e, g, h, i, k - Not propositions: b, d, f, j