A particle is moving eastwards with velocity of `5 m//s`. In `10 sec` the velocity changes to `5 m//s` northwards. The average acceleration in this time is.
A. Zero
B. `(1)/(sqrt(2))ms^(-2)` towards north-west
C. `(1)/(sqrt(2)) ms^(-2)` towards north-east
D. `(1)/(2) ms^(-2)` towards north