The correct answer is: gravity.
The complete sentence is:
"
A person on earth would weigh a lot more on the sun due to increased gravity"
In fact, the weight of a person is given by

where m is the mass of the person, while g is the gravitational acceleration. While the mass m of the person does not change moving from Earth to the Sun, the gravitational acceleration g does depend on the mass of the planet/star. In fact:

where G is the gravitational constant, M is the mass of the planet/star, r is its radius. Due to the fact that the mass of the sun is huge compared to the Earth's mass, the gravitational acceleration at the Sun's surface is much more than the gravitational acceleration at Earth's surface, so a person would weigh much more on the Sun than on Earth.
(by comparison, the value of g at the Sun's surface is approximately 28 times the value of g at Earth's surface).