Explanation

Smoking (especially of tobacco or cannabis) is often considered a gateway behavior that can lead to experimenting with harder substances.

It is widely observed as a first step in the path toward more serious drug addiction.

Explanation

The galactic bulge is the dense, bright central region of a spiral galaxy, including our Milky Way.

It contains older stars and a supermassive black hole at its core.

Explanation

Observation is the second step where scientists collect facts using senses or tools.

It leads to forming a hypothesis, a possible explanation to be tested.

The Steps of the Biological Method:

1. Recognition of a problem
2. Observation
3. Hypothesis formation
4. Deduction
5. Experimentation
6. Data collection and analysis
7. Conclusion
8. Theory/law formation (if repeatedly confirmed)

Explanation

Euglena is a unicellular organism, a key characteristic of many Protista.

Although it is eukaryotic and lives in water, being unicellular is the main reason it’s classified under Protista.

Explanation

One human leg has 31 bones including the femur, tibia, fibula, patella, tarsals, metatarsals, and phalanges.

These bones support movement and bear the body’s weight.

Explanation

Water makes up about 70% of the cell's composition.

It is crucial for various cellular processes, including biochemical reactions and maintaining cell structure.

Explanation

In terrestrial ecosystems, plants are the main producers that convert sunlight into energy via photosynthesis.

They form the base of the food chain and support all other life forms.

Explanation

White blood cells (WBCs) are the body's defense cells that fight infections and diseases.

They identify and destroy harmful bacteria, viruses, and other pathogens.

Explanation

The speed of sound in water is approximately 1500 meters per second, much faster than in air (~343 m/s).

Sound travels faster in denser media like liquids and solids, and cannot travel in a vacuum.

Explanation

Abdul Qasim Ali Zahravi, also known as Al-Zahrawi, is considered the father of modern surgery.

He wrote the influential medical encyclopedia Al-Tasrif, which included surgical techniques.