Select the most appropriate sentence with respect to grammar and usage.
1
Sunflower sea stars are vital in maintain a diverse ocean ecosystem.
2
Very little is knowing about the life cycle of the starfishes because the larvae are so tiny that they are very hard to monitor.
3
The Earth absorbs sunlight, then radiates it as heat.
4
Air pollution not only put a large burden on human health but also affects the climate on a large scale.
5
None of these