Which of the following statements is true?

plants use flowers for reproduction.
the sun's gravitational pull keeps the planets in orbit.
mammals are the only animals that give birth to live young.
all of the above

c. establishing proper sleep hygiene

instead of copying and pasting things off of tests or work done on computer which im sure you did, try and read over the question carefully

option d : from a warmer substance to a cooler substance

according to second law of thermodynamic, heat flows from higher to lower temperature region. heat is the transfer of energy from an object at higher temperature to an object at a lower temperature. so energy flows from warmer to colder objects.