Explanation:

- Option 1: Coplanar vectors

Vectors that lie in the same plane are called coplanar vectors. They might be zero or non-zero, and it's not about being non-zero.

- Option 2: Proper vectors

All non-zero vectors are called proper vectors. Zero vector is considered an improper vector. So, "proper vectors" refers to any vector that isn't the zero vector.

- Option 3: Co-initial vectors

Co-initial vectors are those that have the same initial point. This is about position, not about being non-zero only.

- Option 4: Equal vectors

Equal vectors have the same magnitude and direction, regardless of where they are. Again, it's not about being non-zero alone.

So, the correct answer is:

Option 2: Proper vectors