I like Oranges, do you?

The answer can also be $3$ . If in the first case, the first bullock eats $10$ oranges in first minute, the second bullock eats $10$ oranges in the second minute, and so on, then they can eat $80$ oranges in $8$ minutes. So in the second case, where $3$ bullocks are involve, they can eat the $30$ oranges in $3$ minutes which is one of the choices.

If 8 bullocks can eat 80 oranges in 8 minutes, then

1 bullock can eat 10 oranges in 8 minutes, and

3 bullocks can eat 30 oranges in the same 8 minutes!

(We can even choose (and separate and/or observe) 3 of the 8 bullocks and will see that they ate

$\frac {3}{8} × 80 = 30 \text { oranges during this 8 minutes!)}$