HELP I GIVE BRAINLIST which of the following is a abiotic factor ?

A ) pH level of water
B ) Coral Reef
C ) fish
D ) seaweed

What produces light and all other electromagnetic waves? a) the photoelectric phenomena b) heated metals c) charged particles d) radioactive samples (pls explain if you can : )

Which of the following are guidelines to follow for obtaining accurate observations

Question 1 (5 pts): what is the maximum distance for which you can you resolve the two individual headlights of an on-coming truck as two separate lights rather than one if the headlights are separated by 2.00 m and your eye has a diameter of 1.00 centimeter? assume a wavelength of 500 nm.