One of the exceptions to the warrant requirement involves exigent circumstances.. What is the ...

One of the exceptions to the warrant requirement involves exigent circumstances.. What is the meaning of exigent circumstances?
 
  a. Police may conduct warrantless searches when granted consent to search by someone with actual or apparent authority to grant such consent.
  b. Police may conduct warrantless searches when incident to a lawful arrest.
  c. Police may conduct warrantless searches when probable cause exists to search a motor vehicle.
  d. Police may conduct warrantless searches when emergency situations make it impracticable for police to seek and obtain a warrant first.