The nucleus of an atom contain protons and neutrons, which make up most of the mass of an atom.
The answer would be 2 and 3 ( 2nd answer choice)
Because it can cause serious infections in the lungs, blood and our brains...It may also cause urinary tract and infections in wounds.
New moon, quarter moon, full moon are what we call the lunar phases. These are consequences of the motions of the Sun, Earth and moon. Three dimensional models are useful because the face of the moon that catches the light of the Sun depending on their position at any given time could be depicted well. Circular models would be the best visuals for the lunar phases.
The numbers 3 and 4 means that there are 3 Nitrogen atoms, and 12 Hydrogen atoms in the chemical formular (3NH4). The 3 coefficient in front of the compound applies to all of the elements while the 4 applies to only hydrogen (H). This means that the compound contains 3 Nitrogen atoms and 12 (4 multiplied by 3) Hydrogen atoms.