Which pair of organisms consists of producers?

The correct answer is Option (1) → Plants and phytoplankton

Producers are the green plants of an ecosystem. They make their own food by photosynthesis, so all other organisms depend on them. On land the major producers are herbaceous and woody plants. In water the producers are phytoplankton, algae and higher plants.

Option (1) Plants and phytoplankton — Correct. Plants (on land) and phytoplankton (in water) are both producers.

Option (2) Plants and consumers — Incorrect. Consumers are heterotrophs. They feed on producers or on other animals, so they are not producers.

Option (3) Zooplankton and phytoplankton — Incorrect. Phytoplankton are producers, but zooplankton are consumers. In a pond, the zooplankton feed on other organisms.

Option (4) Phytoplankton and chlorophylls — Incorrect. Chlorophylls are pigments found in producers. They are not organisms, so they cannot form a pair of organisms.

NCERT Extract:
Energy Flow – “… The green plant in the ecosystem are called producers. In a terrestrial ecosystem, major producers are herbaceous and woody plants. Likewise, producers in an aquatic ecosystem are various species like phytoplankton, algae and higher plants.”
Ecosystem – Structure and Function – “… The autotrophic components include the phytoplankton, some algae and the floating, submerged and marginal plants found at the edges. The consumers are represented by the zooplankton, the free swimming and bottom dwelling forms.”