The answer is d because i had the same problem yesterday in biology
Answer:
• An acid is an electrolyte that hydrolyses in water to release hydrogen ions.

• pH level of an acid;
- Strong acid → 0 - 3.8
- Weak Acid → 4.0 - 6.7
E=hv is an equation important when dealing with light. E refers to the energy of a photon; h is Planck's constant and v is the wavelength. According to this equation, light particles called photons travels in packets of energy. This is important in pv cells because this is the technology used to harness solar energy which is converted to electricity. The amount of energy should be estimated to know the appropriate material of construction of the pv cell to achieve optimum conditions. In this way, the pv cell could maximize the sun's energy.
A star is formed within the clouds of dust. These clouds of dust are scattered throughout the galaxy. These dust clouds are called as nebula. The turbulence inside the dust clouds rise to form knots. These knots along with sufficient mass causes gas and dust to collapse with the help of gravitational force. These sequence of steps leads to form a star.
Displacement is shortest distance from starting point, 4km.