1. Azotobacter is one of the nitrogen-fixing bacteria used as a biofertilizer.
2. They have to be applied to the leaves of the plant only.
3. They alter the chemical composition of the soil.
4. They can be used along with organic fertilizers.
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1. Warm-blooded animals can remain active in a cold environment in which cold-blooded animals can hardly move.
2. Cold-blooded animals require much less energy to survive than warm-blooded animals.
Which of the statements given above is/are correct?

1. They are steroids, proteins, peptides, or amino acids derivatives.
2. They are not produced by body organs and are mostly taken as supplements.
3. They do not influence the working of those organs which have secreted them.
4. They act as co-enzymes and help enzymes to perform their function.
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