B- Enzymes act as catalysts to speed up chemical reactions
Answer: The Pulmonary Arteries
Explanation: They are two pulmonary arteries with on serving each human lungs, which brings deoxygenated blood to the lungs from the hilium. The arteries go into the capillaries of the alveoli. Capillaries are the thinnest ,smallest blood vessel,they supply oxygen to single tissues in all parts of the human body.
<span>Vertebrates and invertebrates</span>
Three factors that determine the reactivity of elements are the
valence electrons are the electrons in the outermost electron shell of an atom.
The number of electrons in an atom's outermost valence shell governs its
bonding behaviour. That is why in periodic table the elements were put together
according to their numbers of valence electrons.
METALS
The most reactive kind of metallic element is a metal from
Group 1 sodium or potassium.
An atom in Group 1 has only one valence electron.
NON-METALS
A nonmetal tends to attract another valence electrons to
attain a full valence shell.
