Explanation

Pathogenic bacteria are harmful microorganisms that cause diseases in humans, animals, or plants.

Examples include E. coli, Salmonella, and Streptococcus.

Explanation

2H₂ + O₂ → 2H₂O

This balanced equation ensures 4 hydrogen atoms and 2 oxygen atoms on both sides.

It correctly represents the formation of water from hydrogen and oxygen gases.

Explanation

A hand drill uses two mutually perpendicular gears to convert rotary motion.

This mechanism increases torque and helps in efficient drilling.

Explanation

Children under 5 are most vulnerable to waterborne diseases due to their developing immune systems and high susceptibility to dehydration.

Poor sanitation and contaminated water sources can severely impact young children, leading to high mortality rates in this age group.

Explanation

Ammonia (NH₃) has a trigonal pyramidal shape due to one lone pair on the nitrogen atom.

The molecular geometry results from sp³ hybridization and lone pair-bond pair repulsion.

Explanation

Sodium is a reducing agent because it loses electrons easily.

Oxidizing agents gain electrons; chlorine, nitric acid, and nitrogen can act as oxidizers, but sodium cannot.

Explanation

Green plants make their own food through photosynthesis, so they are called producers.

They form the base of the food chain in any ecosystem.

Explanation

Pheretima posthuma is the common species of earthworm found in South Asia.

It belongs to the phylum Annelida.

It is important for soil fertility.

Explanation

During swimming, knees and ankles play a key role in kicking movements.

These joints allow flexion and extension, providing thrust in the water.

Explanation

Heart muscle (cardiac muscle) contracts automatically without conscious control — it's involuntary.

Neck and leg muscles are voluntary and controlled by conscious effort.