Final answer:
The statement is true; Mars' lower surface gravity allows its volcanoes to grow taller, as exemplified by Olympus Mons, aided by the stationary nature of the Martian crust over volcanic hot spots.
Step-by-step explanation:
The statement, 'The low surface gravity helps Martian volcanoes grow to great heights', is true. The surface gravity on Mars is approximately one third of that on Earth, which means that the internal strength of a mountain on Mars can be less, and yet still support a greater height against the force of gravity.
Olympus Mons, the largest volcano on Mars, reaches more than twice the height of Earth’s tallest mountains because of this lower gravity. Additionally, the Martian crust remains stationary over hot spots for long periods, allowing volcanoes such as Olympus Mons to grow substantially over hundreds of millions of years, unlike the moving crustal plates on Earth that form chains of smaller volcanoes.