Which option shows the correct mental steps to find the sum of $38 + 19$ using the 'add and adjust' shortcut?

$38 + 20 = 58$, then $58 - 1 = 57$

$38 + 20 = 58$, then $58 + 1 = 59$

$38 + 10 = 48$, then $48 + 9 = 57$

$30 + 10 = 40$, then $8 + 9 = 17$, then $40 + 17 = 57$

When calculating $42 + 19$ by first finding $42 + 20$, why must we subtract 1 from the result?

Because we added 20, which is 1 more than 19.

Because we must always subtract after adding.

Because the answer has to be an odd number.

Because we rounded the number 42 up.