[fast please, no links] "Complete a combining ratio of Lithiym and Oxygen."

Also what is a combining ratio and how do you write one? I never learned this

What rule is used to determine how many covalent bonds an element can form? a. the number of covalent bonds is equal to six c the number of covalent bonds is equal to five minus the group number plus the group number b. the number of covalent bonds is equal to eight d. none of the above minus the group number select the best answer from the choices provided