Let v1 = , and v3 = does (v1, v2.v3 span r4? why or why not? 0 choose the correct answer below. a. yes. any vector in r4 except the zero vector can be written as a linear combination of these three vectors. o b. no. when the given vectors are written as the columns of a matrix a, a has a pivot position in only three rows. o c. no. the set of given vectors spans a plane in ir4. any of the three vectors can be written as a linear combination of the other two. 0 d. yes. when the given vectors are written as the columns of a matrix a, a has a pivot position in every row.