MCQ
Phytohormones are:
- ✓Regulators synthesized by plants and influencing physiological processes.
- BHormones regulating growth from seed to adulthood.
- CChemicals regulating secondary growth.
- DChemicals regulating flowering.
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($i$) It consists of a network of trachea, that open through $12$ pairs of small holes called spiracles present on the lateral side of the body.
($ii$) Thin branching tubes carry oxygen from the air to all the parts.
($iii$) The opening of the spiracles is regulated by sphincters.
($iv$) Exchange of gases take place at the tracheoles by diffusion.
Choose the correct combination of $A$ and $B$