Help me please

Which best describes the nucleus of an atom a. it is where all of the particle s of the atom are located b. it is the negatively charged part of the atom c. it is where the electrons and the protons are located d. it is the part of the atom with the greatest mass

Which cell organelle is the site for photosynthesis? a. chloroplast b. endoplasmic reticulum c. golgi apparatus d. lysosome

If you relate the doppler effect on sound to the color of light waves, a police car would be the color as it approaches and the color as it recedes away from the observer.