Question on who vs. whom

Question on who vs. whom References I answered two questions incorrectly during my SAT prep class, and they seem to contradict each other. The first question was: The district manager agreed to promote the employee who he saw improve sales by the end of the year. (A) who he saw improve (B) who he saw was improving (C) who he will see improve (D) whom he saw improve (E) whom he saw to be improving I picked A but the correct answer was D. Now, for my second question: During the auditions, the show\'s producer looked for those actors whom he thought would be suitable for the many roles in the play. (A) whom he thought (B) whom he has thought (C) who he was thinking (D) who he thought (E) whom they thought Again, I picked A here but the the correct answer was D. I don\'t understand why one uses \"who\" while the other uses \"whom\", since they seem to have the same sentence structure (but obviously different words).