Agglutination of erythrocytes of donor will occur ifa. O is given to AB b. O is given to A c. O is given to B d. B is given O

Of course, here are step-by-step solutions to a sample problem: \textbf{Problem:} Simplify the expression $\frac{3x^2-9x}{6x}$. \textbf{Solution:} Step 1: Factor out the greatest common factor of the numerator. $\frac{3x^2-9x}{6x}=\frac{3x(x-3)}{6x}$ Step 2: Simplify the fraction by canceling out the common factor of 3 and dividing by 6. $\frac{3x(x-3)}{6x}=\frac{x-3}{2}$ Step 3: Check for any restrictions on the variable. Since the original expression has a denominator of $6x$, we must make sure that $x\ne 0$ in order for the simplified expression to be defined. Therefore, the final answer is: $\boxed{\frac{x-3}{2},x\ne 0}$ Note that we have included the restriction on the variable in our answer, as it is important to make sure the simplified expression is valid for all possible values of $x$.