What stage is represented by letter X in the above diagram?

The question asks to identify the natural source of heat from the given diagrams.

• M is a flashlight, which is an artificial source of light and heat.
• N is burning wood/fire, which can be natural (like a forest fire) or artificial (like a campfire).
• P is the Sun, which is a natural source of heat and light.
• Q is a stove, which is an artificial source of heat. Among the given options, the Sun (P) is unequivocally a natural source of heat.

The correct option is C.

The question asks which parts of a house allow air to enter.

• A: Doors allow air, but walls generally do not.
• B: Windows can be opened to allow air, and air vents are specifically designed for air circulation. This is correct.
• C: Doors allow air, but roofs generally do not.
• D: Walls generally do not allow air, though air vents do. The most common and intended parts of a house that allow air to enter are windows and air vents.

The correct option is B.

The diagram shows the life cycle of a frog. The sequence shown is:

• Toad (Adult frog) lays eggs.
• Eggs hatch into Tadpoles.
• Tadpoles develop into Froglets (young frogs).
• Froglets grow into Toads (Adult frogs). The arrow points from "Toad" (Adult frog) to "X", and then from "X" to "Tadpole". This indicates that "X" is the stage immediately after the adult frog and before the tadpole. This stage is the Eggs.

The correct option is C.