Assertion: Oxygenic photosynthetic bacteria (cyanobacteria) generate oxygen as a by-product of photosynthesis, yet some are able to fix nitrogen as well.
Reason: These are colonial bacteria that have specialized cells (heterocysts) that lack the oxygen generating steps of photosynthesis.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Consider the following two facts regarding mycorrhizae:
A. The percent of plant species that form ectomycorrhizae
B. The percent of plant species that form arbuscular mycorrhizae

1.(A) is greater than (B)
2. Item (A) is less than item (B)
3.(A) and (B) are approximately equal
4. A & B have no relationship