ANS:C - W 90°

Let us assume, WBC=30°, We can say In Reduced bearing is = N 30° E.
Another one assumes WBC=60°, can say in reduced bearing= E 30° N.
So, we can see which quadrant is nearest the angle is first written on a paper then the degree then the direction.
Hence, according to the question, the nearest is exact on W 90°. Reduced bearing is always from the closest north or south, but in this case, N90W and S90W both are equidistant so option A and B is rejected. When we don't take reference either from north or south, we have to specify W but with W90 is given in option So we go for option C. If the line is along the north direction it is mentioned as N0° or due north.
If the line is along the south direction it is mentioned as S0° or due south.
If the line is along the east direction it is mentioned as N90°E or S90°E or due east.
If the line is along the west direction it is mentioned as N90°W or S90°W or due west.
In ques, it is given 270° means west direction. If you see from both references N and S than it is same so confusion occurs.
If you write 90 W then it will be same as showing declination.
Due to this, all reason at this point answer is W 90.

Similarly,
0° = N 0,
180° = S 0,
90° = E 90,
270° = W 90.