The correct answer is option 4: Lichens. Lichens are the first organisms to colonize a bare rock. Lichens are unique organisms composed of a symbiotic relationship between fungi and algae or cyanobacteria. They have the ability to survive in extreme environments, including bare rocks, due to their ability to withstand harsh conditions such as intense heat, lack of water, and strong winds.

Option 1: Algae alone - While algae can also colonize rocks, they typically require a moist environment and are not as resilient as lichens in harsh conditions.

Option 2: Ferns - Ferns require soil to grow and cannot colonize bare rocks as they need a well-established substrate.

Option 3: Fungi alone - Fungi can break down rocks over time and aid in creating soil, but they are not typically the first organisms to colonize bare rocks.

In conclusion, lichens are the first organisms to colonize bare rocks due to their resilience and ability to survive in extreme conditions.