A particle is moving eastwards with a velocity of \[5\text{ }m{{s}^{-1}}\]. In 10 seconds the velocity changes to \[5\text{ }m{{s}^{-1}}\] northwards. The average acceleration in this time is

• A. \[\frac{1}{2}m{{s}^{-2}}\] toward north
• B. \[\frac{1}{\sqrt{2}}m{{s}^{-2}}\] toward north-east
• C. \[\frac{1}{\sqrt{2}}m{{s}^{-2}}\] towards north-west
• D. zero