New crust forms: a. at the asthenosphere. b. near a convergent boundary. c. where two plates collide. d. at ocean ridges.

New crust forms D. at ocean ridges .

At mid-ocean ridges, there is separating of plate tectonics allowing the formation of new crust from the cool solid magma. The process leads to the formation of the new seafloor and it is called the new seafloor spreading.  

Since the earth is not expanding to make way for spreading seafloor, at the subduction zone, the tectonics sink back into lithosphere or earth's interior. The new crust formation at ocean ridges can be a slow or fast process. Some ridges spread at 2 inches (5 centimeters) per year while others spread at 6 inches (15 Centimeter) per year.

The correct answer is option D. at ocean ridges.

Explanation:

New oceanic crust is continuously forming while magma appears at mid-ocean ridges.

Age and the rate of spread determine the characteristics of an oceanic crust.

The study of the crust is easy to carry out because it is now exposed on land, since it has been formed millions of years ago. Although still a large amount of oceanic crust remains underwater. Therefore, any type of new crust is initially generated at ocean ridges.