496: The tendency of a liquid drop to contract and occupy minimum area is due to
(a) viscosity
(b) surface tension
(c) density
(d) vapour pressure
497: Photo chemical smog is a resultant of the reaction among.
(a) NO2, O3 and peroxyacetyl nitrate in the presence of sunlight
(b) CO, O2 and peroxyacetyl nitrate in the presence of sunlight
(c) CO, CO2 and NO2 at low temperature
(d) High concentration of NO2, O3 and CO in the evening
Explanation:
First statement is true Photo chemical smog is the chemical reaction NO2, O3, peroxyacetyl nitrate and sunlight.
498: Snake bite first affects the:
(a) Nervous system
(b) Blood circulation
(c) Brain
(d) Lungs
499: Consider the following minerals:
1. Calcium
2. Iron
3. Sodium
Which of the minerals given above is/are required by human body for the concentration of muscles?
(a) 1 only
(b) 1 and 3 only
(c) 2 and 3 only
(d) 1, 2 and 3
Explanation:
Calcium is necessary for muscle contraction
Iron is present in the muscle in the form of myoglobin. Myoglobin stores oxygen and this oxygen is used for muscle contraction.
Sodium helps nerve cells send electrical signals to muscles for contraction.
500: Significantly higher level of urea in the blood is the indication of
(a) Liver damage
(b) Kidney damage
(c) Heart attack
(d) Spleen damage