Explanation

An element with 7 valence electrons needs 1 more electron to complete its octet.

Therefore, its valency is 1, as it tends to gain 1 electron during bonding.

Explanation

• On Earth, surface water covers 70% area.
• 70-71 percent of the Earth's surface is water-covered.
• The oceans hold about 96.5 percent of all Earth's water.
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• This includes oceans, rivers, lakes, glaciers, and groundwater.
  

Explanation

An aqueous solution is one where the solute is dissolved in water.

"Aqua" means water, making it the key solvent in such solutions.

Explanation

Photosynthesis requires carbon dioxide, water, and sunlight, not oxygen.

Respiration, rusting, and combustion all need oxygen to occur.

Explanation

Water (H₂O) is a pure compound, not a mixture.

Tea, air, and alloys are mixtures of different substances.

Explanation

Sodium is a chemical element with the symbol Na and atomic number 11.

It is a soft, silvery-white, highly reactive metal.

Sodium is an alkali metal, being in group 1 of the periodic table.

Explanation

A food web is formed by interconnected food chains in an ecosystem.

It shows multiple feeding relationships and energy flow among organisms.

Explanation

Sepals are part of the flower that protects the developing bud but do not participate in reproduction.

Pollen grain, ovule, and carpel are directly involved in the reproductive process.

Explanation

Abiotic components are non-living parts of the environment.

Water vapor is a non-living element.

While beetle, apple, and lion are living organisms.

Explanation

Photosynthesis occurs most efficiently in this temperature range, as enzymes involved in the process function optimally.

Temperatures above 35°C can inhibit enzyme activity, reducing the rate of photosynthesis.