Vectors ` vec a= hat i+2 hat j+3 hat k , vec b=2 hat i- hat j+ hat k` and `vec c=3 hat i+ hat j+4 hat k ,` are so placed that the end point of one vector is the starting point of the next vector. Then the vector are (A) not coplanar (B) coplanar but cannot form a triangle (C) coplanar and form a triangle (D) coplanar and can form a right angled triangle