The vector that must be added to the vector \[\hat{i}-3\hat{j}+2\hat{k}\] and \[3\hat{i}+6\hat{j}-7\hat{k}\] so that the resultant vector is a unit vector along the y­­-axis is

• A.            \[4\hat{i}+2\hat{j}+5\hat{k}\]
• B.                                      \[-4\hat{i}-2\hat{j}+5\hat{k}\]
• C.            \[3\hat{i}+4\hat{j}+5\hat{k}\]                                         
• D.  Null vector