Final answer:
Quantum physics is difficult to apply to macroscopic objects due to quantum fluctuations, decoherence, and entanglement. These phenomena are significant at the quantum level but diminish with larger systems where classical mechanics dominate.
Step-by-step explanation:
Quantum physics is challenging to apply to macroscopic objects for several reasons. The correct answer to this question is option (a): Quantum fluctuations, decoherence, and entanglement. Here's a brief explanation of each: Quantum fluctuations refer to the temporary change in the amount of energy in a point in space as allowed by the Heisenberg Uncertainty Principle. This phenomenon is significant on the quantum level but becomes negligible when considering larger systems where classical mechanics reign. Decoherence is the process by which quantum systems lose their quantum behavior (like superposition and entanglement) and transition into an incoherent mixture of states that can be described by classical physics.
For macroscopic objects, interactions with the environment cause rapid decoherence effectively washing out quantum effects. Entanglement is a peculiar quantum phenomenon where particles become linked and the state of one instantaneously affects the state of another no matter the distance between them. In macroscopic objects, this entanglement is typically not observed because it is extremely delicate and easily disrupted by environmental interactions. The principles of quantum mechanics such as wave-particle duality can be counterintuitive when compared to everyday experiences with macroscopic objects. As per the correspondence principle suggested by Niels Bohr classical mechanics serves as an approximation of quantum mechanics for macroscopic systems with large energies.