When does the placenta begin to form?
O
A. In the second trimester
O
B. At the end of the third trimester
O
C. A few days after fertilization
O
D. At the end of the first trimester

A few days after fertilization

Explanation

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds