(i) Nerve impulse travels in one direction Since the neurotransmitter is present only in the axon terminal so nerve impulse always travels from the axon terminal of one neurone to the dendrite or cell body of the next neurone.

(ii) Jamming of wooden doors and windows takes place during rainy season The cellulose of the wood absorbs water and swells up. This causes increase in size of doors and windows resulting in jam.

(iii) A cut plant wilts fast even if the cut end is dipped in water As the rate of transpiration is higher than that of the absorption by the cut end, the wilting is fast.

(iv) Urine excreted during summer months is hypertonic During the summer, excessive water is lost as sweating. Urine becomes hypertonic to reduce the loss of water in urine and maintains the osmotic concentration of the blood constant.

(v) A person has difficulty in focusing on nearer objects as the age increases With the advancement of age, the elasticity of the lens decreases. It causes the person difficult to focus the nearer object.