I am in need of help please

Iwill give brainliest if you answer right : )

An equinox occurs when a. neither end of earth's axis is tilted toward or away from the sun. b. the north end of earth's axis is tilted away from the sun. c. the north end of earth's axis is tilted toward the sun. d. earth's axis is parallel to the sun's rays. select the best answer from the choices provided a b c d

Why is it important always to use horizontal bars in unit fractions when performing unit conversions?