Which of the following best describes why Congress approved the Tonkin Gulf Resolution in 1964?
A) Congress members wanted to limit the president's war making powers
B) Congress members wanted to give the president the sole power to declare war
C) Lyndon Johnson misled them
D) the U.S. ship Maddox had been the target of an unprovoked attack
To answer this, you will really need to look at your text. Depending on one's perspective and how one uses words like "misled," either C or D could be correct. Your book presumably has a sentence or two that clearly states which of those is right.
It is not at all clear that the USS Maddox really was attacked. However, most people in 1964 believed that it (and later the Turner Joy) had been attacked. In fact, Pres. Johnson was criticized for not reacting more strongly to the Maddox attack. Therefore, most members of Congress would have believed that an unprovoked attack had happened.
Pres. Johnson did, in a sense, mislead Congress. He made statements to them about the attack that turned out not to be true. As the link below says, he later acknowledged that the attacks might not have happened:
Years later, however, Johnson admitted that the initial reason for the resolution—the alleged North Vietnamese attack of August 4—probably never even took place. "For all I know, our navy was shooting at whales out there," he said.
However, there is no real evidence to suggest that Johnson knew this in 1964.
So, the answer to this depends on how you want to look at things. D is probably not true because the attack might not have happened. But that was not known in 1964. Johnson probably misled Congress, but not, I would argue, knowingly or purposely. So C is sort of right and sort of wrong.
Again, you really should check to see what your book says.