_____ are massive objects destined to become planets.
A) Planetesimals
B) Protoplanets
C) Preplanets
D) Pseudoplanets
Question 2
Which of the following statements is true in the context of radioactive elements?
A) The abundances of the daughter isotopes of radioactive elements in a rock gradually decrease.
B) The abundance of a radioactive element in a rock gradually decreases.
C) Uranium-238 has the longest half-life among all the other radioactive substances.
D) Potassium-40 has the longest half-life among all the other radioactive substances.