In Iago's opening soliloquy, he suggests that his success in manipulating Othello is primarily a result of?

Othello's natural tendency.

Explanation:

The Tragedy of Othello, the Moor of Venice is a play written by William Shakespeare. The play is a tragedy that narrates the trick that has been played on Othello of his wife being convicted of adultery.

Othello's wife, Desdemona, is blamed for adultery by Iago. In Iago's opening soliloquy, the readers and audience get to know that he plans to take revenge on Othello because he believed the rumors that his wife, Emilia, has slept with Othello.

From his soliloquy, we get to know that Iago was able to trick Othello of his wife's infidelity because of the natural tendency of Othello. Othello has been an insecure husband when Desdemona pleaded Othello to not punish Cassio, the manipulation of Iago worked even more effectively.

So, the correct answer is Othello's natural tendency.