Answer:
a. These four vectors are dependent because there are columns of 3 by 4 matrix with one free variable.
b. If one is a multiple of other
c. c1v1 + c20 = 0 has nontrivial solution.
Explanation:
Any set of 4 or more vectors must be linearly dependent. The non trivial combination of vector may produce zero as the set is linearly dependent. The vector v1 and v2 will be dependent if one is the multiple of the other.