Choose the best estimate for the product 68x7.

The correct option is C 490
68 is close to 70.
$\therefore$ The product $68\times 7$ is best estimated by the product $70\times 7,$ which is 490.

Verification

$568\underset{–}{7}\times \underset{–}{476}$

476 is indeed close to 490. Thus, 490 is a good estimate.