Option c is correct.
Most of the organic toxins are water insoluble and non-biodegradable.
These high persistent toxins are, therefore, transferred from lower trophic level to higher trophic level through food chain.

1, 2, 3 and 4 are correct.
Ozone layer depletion increases the amount of UVB that reaches the Earth’s surface. Laboratory and epidemiological studies demonstrate that UVB causes non-melanoma skin cancer and plays a major role in malignant melanoma development.
UVB radiation affects the physiological and developmental processes of plants.
Phytoplankton form the foundation of aquatic food webs. Phytoplankton productivity is limited to the euphotic zone, the upper layer of the water column in which there is sufficient sunlight to support net
productivity. Exposure to solar UVB radiation has been shown to affect both orientation and motility in phytoplankton, resulting in reduced survival rates for these organisms. Scientists have demonstrated a direct reduction in phytoplankton production due to ozone depletion-related increases in UVB. Synthetic polymers, naturally occurring biopolymers, as well as some other materials of commercial interest are adversely affected by UVB radiation.

A biome is even bigger than an ecosystem. A biome is a large geographical area that contains distinct plant and animal groups which are adapted to live in that environment. There can be many different habitats in a biome.
Some major biomes are tundra, taiga, grasslands, deciduous forest, fresh water, desert, alpine, rainforest and ocean.

Indicator species, organism—often a microorganism or a plant—that serves as a measure of the environmental conditions that exist in a given locale.
Example – Lichens: Quality of air can be determined based on its presence.

All the above organisms are involved in nitrogen cycle.