whether the following statements are true or false. Explain why. Assume that a relation schema R(A..... An) is given and that XC (A,..... An) holds. For t Erg. let t[X] be the projection of t to the attributes in X. X is called a key if the following condition is fulfilled: For all relation instances r of R holds: V t, t ErR: t[X] = t[X]) t = t2- In Relational Algebra, the order of operations does not matter when performing a query.