# A particle has an initial velocity $3 \hat{i} + 4 \hat{j}$ and an acceleration of $0.4 \hat{i} + 0.3 \hat{j}$. Its speed after 10 s is
( A ) $8.5$ units
( B ) $10$ units
( C ) $7 \sqrt{2}$ units
( D ) $7$ units