Three vectors A, B, and C add up to zero. Then:

1. vector (A×B)×C is not zero unless vectors B and C are parallel.
2. vector (A×B).C is not zero unless vectors B and C are parallel.
3. if vectors A, B and C define a plane, (A×B)×C is in that plane.
4. (A×B).C = |A||B||C|  → C2 = A2 + B2


The incorrect statement/s is/are:

1. (b, d)
2. (a, c)
3. (b, c, d)
4. (a, b)

(1) Hint: The resultant of three vectors will be equal to zero only if the vectors are coplanar.

Step 1: Find if the vectors are coplanar.

Given, A + B + C = 0

Hence, we can say that A, B, and C are in one plane and are represented by the three sides of a triangle taken in one order.
Step 2: Find the incorrect statements one by one.

      B×(A+B+C)=B×0=0 B×A+B×B+B×C=0 B×A+0+B×C=0 B×A=B×C A×B=B×C (A×B)×C=(B×C)×C

It cannot be zero as (B×C)×C can not be zero unless B and C are parallel to each other. Hence statement (a) is correct.

If B and C are not parallel, then (AxB) will be perpendicular to the plane of A, B and C.
Hence, (AxB).C = 0 whatever be the situation is. Hence, statement (b) is incorrect and option.
Also, (AxB)xC
will be in the plane of A, B and C and statement (c) is correct.
Statement (d) is also incorrect as discussed already.