William finds a piece of pure iron in his garden. after a few days, the iron begins to rust. what are the two types of substances involved in the rusting process of iron? iron with one kind of atom that combines with oxygen from the air to form rust( iron rust contains two types of atoms, which means it 1)-a compound - an element - a mixture 2)-a compound -an element -a mixture

The first can be filled with an element and the second blank can be filled with a compound.  

Iron is an element as it contains only one kind of atom, which combines with the oxygen from the air to produce rust, that is, iron oxide. The rust comprises two kinds of atoms, which signifies that it is a compound. A compound refers to a molecule that comprises at least two types of atoms. In the case, iron oxide is a compound as it comprises Fe and O atom.  

element then compound

Explanation:

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.

i guess because there isn't enough love going around. < 3