Let `A( vec a)a n dB( vec b)` be points on two skew lines ` vec r= vec a+lambda vec pa n d vec r= vec b+u vec q` and the shortest distance between the skew lines is `1, w h e r e vec pa n d vec q` are unit vectors forming adjacent sides of a parallelogram enclosing an area of 1/2 units. If angle between`A B` and the line of shortest distance is `60^0,` then `A B=` a. `1/2` b. `2` c. `1` d. `lambda R={10}`