The nuclei of continental masses were formed by......... A- deposition of limestone reefs B- meteorite bombardment C- accretion D- Subduction

The correct answer is C- accretion.

Here's a step-by-step explanation:

1. The formation of continental masses, also known as continents, begins with a process called accretion.

2. Accretion is a process in which dust and gas floating through space gradually come together due to gravitational attraction to form larger bodies. This is the initial step in the formation of celestial bodies, including planets and continents.

3. Over time, these larger bodies cool and solidify, forming the nuclei of continental masses.

4. The other options, deposition of limestone reefs (A), meteorite bombardment (B), and subduction (D) are processes that can contribute to the growth and change of continents over time, but they are not responsible for the initial formation of the continental nuclei.