To keep the body healthy, every adolescent needs to have a healthy diet, exercise and hygiene.
Healthy diet:
Adolescence is a stage of rapid growth and development. Hence a diet with proper calories and other nutrients is needed for proper growth and physical activity. A balanced diet is required which includes proteins, carbohydrates, fats and vitamins in requisite proportions. Apart from this, the body needs calcium, phosphorus, iodine and iron because there is an increase in skeletal mass and blood volume during adolescence.
Physical exercise:
Walking, playing outdoor games and doing exercise keep the body fit and healthy. It leads to mental peace.
Hygiene: 
i) Have a bathrobe or twice a day, paying special attention to underarms, groins and genitals.
ii) Change the underwear daily. It should be made of cotton and washed and cleaned everyday.
iii) For adolescents, the increased activity of sweat glands sometimes enhances body odor. If cleanliness is not maintained there are chances of having fungal, bacterial and other infections.

Muscles are of three types
(i) Striated Muscles
1. These are also called as skeletal muscles or voluntary muscles
2. These are multi nucleated, and unbranched.
3. These are attached to bones.
4. Striated muscles are found in arms, legs, neck.
ii) Non-striated Muscles
1. These are also called as smooth muscles or involuntary muscles.
2. They possess single central nucleus.
3. Non-striated muscles are attached to soft parts of the body like blood vessels, iris, bronchi and the skin.
iii) Cardiac muscles
1. These are branched muscles with 1-3 central nuclei
2. These are involuntary muscles.
3. These muscles are found in Heart.

The different types of joints are as follows: 
(i) Immovable joints - Example: Bones of the skull box .
(ii) Partially movable joints - Example: Joints between the ribs and breast-bone.
(iii) Freely movable joints - Example: Hip joint.
(iv) Gliding joint - Example: Ankle bones.
(v) Pivot joint - Example: Joint between axis vertebrae and atlas.
(vi) Hinge joint - Example: Joint between finger bones and toes.
(v) Ball and socket joint - Example: Shoulder joint.

1. Water obtained from different sources like a well, a pond, a river and underground water will always consist of the same two elements hydrogen and oxygen in the ratio 1: 8 by mass. 
2. It obeys the law of constant proportion.

J.J. Thomson found that cathode rays were attracted by the positively charged plate and repelled by the negatively charged plate. This led him to the conclusion that the cathode rays (electrons) were made of negatively charged particles.

It is because the small particles of the cathode rays (electrons) have mass and energy. This energy is used in rotating the paddle wheels.

Spacesuits contain oxygen cylinders and the astronauts carryout artificial respiration to breathe when they go beyond earth's atmosphere. In long term stay in space, Electrolysis of water helps them to generate oxygen.

The coefficient of expansion of gases is large. The gas in the bottle expands to high temperature in summer. Hence the pressure inside the bottle increases. So it bursts when it is opened during summer.

(b) Steel > Water > Wood is the correct statement
Steel has more number of free electrons than water and wood. So it is more electropositive. It has the tendency to gain electrons. So the thermal conductivity of steel is more than water and wood. Like wise, the thermal conductivity of water is more than that of wood.
Thermal conductivity of steel - 43 w/mK
Thermal conductivity of water - 0.606 w/mK.
Thermal conductivity of wood - 0.17 w/mK.

Mass m = 100 kg
Heat capacity C' = \(\frac{\mathrm{Q}}{\Delta \mathrm{T}}=8000 \mathrm{~J} /{ }^{\circ} \mathrm{K}\)
Specific heat capacity C = ?
\( \mathrm{C} =\frac{\mathrm{Q}}{\mathrm{m} \times \Delta \mathrm{T}} \)
\(\mathrm{C} =\frac{\mathrm{C}^{\prime}}{\mathrm{m}}=\frac{8000}{100}=80 \mathrm{~J} \mathrm{~kg}^{-1} \mathrm{~K}^{-1} \)
The specific heat capacity of the vessel is \(80 \mathrm{~J} \mathrm{~kg}{ }^{-1} \mathrm{~K}^{-1} \text { (or) } 80 \mathrm{~J} / \mathrm{kg} \mathrm{K}\)