What is the difference between celestial and terrestrial in planetary terms? someone answer

Density of salty water as compared to the density of pure water is(a) is less(b) is always equal(c) is always more(d) may be less or more

Quantum mechanics applies to subatomic, atomic, nanometer-size, and micrometer-size systems. nanometer, micrometer, and kilometer-size systems. atomic, nanometer-size, and micrometer-size systems. subatomic, atomic, and nanometer-size systems.

What is the force that opposes motion and works against the downward pull? a) friction b) gravity c) weight d) acceleration