Cross out the whole number with a horizontal line and fill in the correct number neatly above the original number.
B cross out the integer with double horizontal lines and fill in the correct number (correct answer) neatly above the original number.
C cross out the wrong number with a single horizontal line and fill in the correct number neatly above the original number.
D cross out the wrong number with double horizontal lines and fill in the correct number neatly above the original number.
Answer analysis: don't fill in numbers and codes. If the number is wrong, cross out the whole number with double lines and fill in the correct number neatly above the original number. Don't change the original number.