The Angels continued to protest, "Do You really want to give the Torah, which You created long before You created the World, to mortal Man? 'Hashem, our Master, How glorious is Your Name in all the Earth, that Your splendor is far above all the heavens - what is Man, that You make mention of him, the Son of Man, that You should take notice of him?" (Psalms, 8)
G-d turned to Moshe and said, "Answer them!"
Moshe said, "Master of the Universe, I am afraid that they will burn me up with the flames in their mouths!"
G-d said, "Hold onto my Throne of Glory, and answer them!
Moshe then said to G-d, "The Torah which You are going to give me, what is written in it?"
G-d answered, "I Am the L-rd your G-d Who took you out of Egypt?"
Moshe turned to the angels, "Did you go down to Egypt? Were you enslaved there? What do you need the Torah for?"
He asked G-d, "What else is in it?"
Hashem answered, "You shall have no other gods!"
Moshe asked the Angels, "Are you living among the non-Jews, who worship idols?"
"What else is in it?"
"Do not take My Name in vain!"
"Are you Angels engaged in commerce, that you should be involved with swearing?"
"Remember the Shabbat to keep it holy!"
"Do you Angels do laborious work, that you should have to be warned not to do it on Shabbat?"
"Honor your father and your mother!"
"Do you angels have parents that you should honor?"
"Don't murder! Don't steal! Don't be immoral!"
"Do any of these apply to you? (Do you eat apples that you should have to make a blessing before you eat them? Do you ride on donkeys that you should have to be warned against wanting to steal the other angel's donkey?" - the last two not said by Rabbi Yehoshua ben Levi, but they seem to be along the same lines)
Immediately, the Angels conceded to Moshe. And each one became a friend of Moshe, and gave him a gift, as it is said, "You went up to heaven, you gathered booty; you took presents for Man." (Psalms, 68) And even the Angel of Death gave Moshe a present - the incense, which wards off plague.
Basically, as Francis Bacon said, "The Proper Study of Man is Man."
The Torah is the set of G-d's instructions for Man and Woman, as to how to lead their lives. It is their Proper Study.