The property of water that causes mosquito larvae to float on it is

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The amount of moisture in the air is termed A. Humidity.
- Explanation: Humidity refers to the concentration of water vapor present in the air.
In which of the following does implantation and development of the embryo take place? B. Uterus.
- Explanation: After fertilization, the embryo implants in the wall of the uterus, where it continues to develop.
The aroma of food can be sensed from a distance by the process of A. Diffusion.
- Explanation: Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration, allowing the scent molecules to spread through the air.
Haemoglobin and oxygen combine to form a compound known as C. oxy haemoglobin.
- Explanation: Oxygen binds reversibly to hemoglobin in red blood cells to form oxyhemoglobin, which is then transported to tissues.
The energy used by living things to carry out life activities ultimately comes from D. the sun.
- Explanation: The sun is the primary source of energy for almost all life on Earth, captured by plants through photosynthesis and then transferred through food chains.
A child suffering from Kwashiorkor lacks A. Protein.
- Explanation: Kwashiorkor is a severe form of malnutrition caused by a deficiency in dietary protein.
Calculate the voltage across a wire of resistance $4\,\Omega$ if $3\,\text{amperes}$ of current is passing through it.

Recall Ohm's Law, which states that voltage ( $V$ ) is the product of current ( $I$ ) and resistance ( $R$ ).
$$ V = I \times R $$
Substitute the given values into the formula.
$$ V = 3\,\text{A} \times 4\,\Omega $$
Calculate the voltage.
$$ V = 12\,\text{V} $$ * The correct answer is **D. $12.00\,\text{V}$**.
20. The color code for a live wire in an electric plug is B. brown. * Explanation: In many modern electrical wiring standards (e.g., in the UK and EU), the live wire is colored brown.
1. Which of the following does not consist of a transistor? C. Pen.
  
  Explanation: Computers, television sets, and sound systems are electronic devices that rely heavily on transistors for their operation, whereas a simple pen does not.
2. The force that exists in a pulled string is A. Tension.
  
  Explanation: Tension is the pulling force transmitted axially by means of a string, cable, chain, or similar one-dimensional continuous object.
3. The property of water that causes mosquito larvae to float on it is C. surface tension.
  
  Explanation: Surface tension is the cohesive force between liquid molecules at the surface, creating a "skin" that can support light objects.
4. A force of $25\,\text{N}$ acts on a surface of area $125\,\text{cm}^2$ . Calculate the pressure exerted on the surface.

    $$
    P = \frac{\text{Force}}{\text{Area}}
    $$

Substitute the given values.
Note that the options use 'N/c', which likely implies $\text{N/cm}^2$ . $P = \frac{25\,\text{N}}{125\,\text{cm}^2}$
Calculate the pressure.
$$ P = 0.2\,\text{N/cm}^2 $$ * The correct answer is **B. $0.2\,\text{N/c}$**.
25. Which of the following is a source of salicylic acid? D. Aspirin. * Explanation: While salicylic acid is naturally found in willow bark, among the given options, Aspirin (acetylsalicylic acid) is a derivative of salicylic acid and is closely associated with it.
1. The only known planet that supports both plant and animal life is C. earth.
  
  Explanation: Earth is the only planet currently known to harbor life.
2. The crown and root of the tooth meet at a point called B. neck.
  
  Explanation: The neck (or cervical line) is the constricted region where the crown and root of a tooth meet.

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