Correct Option - A
For the race to end in a dead heat,
both A and B should reach the winning post at the same time.
A's speed is twice B's speed.
To run the same distance,
time taken by B=2*(time taken by A)
Time taken by B to run 100 m
= 2*Time taken by A to run 100 m
Time taken by B to run 50 m
= Time taken by A to run 100 m
Hence, A can give B a start of 50 m.