All things are made of cells (both algae and daisies are made of cells)
All cells come from pre-existing cells (both bacteria and horse cells had cells that made their cells)
Cells are the smallest unit of life (nothing is smaller than cells not grass cells or fungi cells)
They use radiometry and pyrometry
NASA uses the Transiting Exoplanet Survey Satelite (TESS) telescope that employes this technology
This telescope measures the brightness/luminosity of stars. When this brightness drops regularly, every more or less in the same number of years, then there is the likelihood of a planet orbiting the star. The dip in brightness of the star is directly proportional to the size of the planet and the distance between the star and the orbiting planet.
C.
Hydrosphere refers to all the water on the earths surface therefore making C the only correct answer.