Explanation

The correct sentence is: "Hurry up or you will miss the bus."

"Or" is used to show a warning or consequence — if you don't hurry, the result will be missing the bus.

Explanation

Burning pure hydrogen produces only water vapor as a byproduct, causing no harmful pollution like carbon or sulfur oxides.

Hence, hydrogen is considered a clean fuel with no emission of pollutants such as sulphur dioxide or carbon dioxide.

Explanation

A chemical change alters both the appearance and the composition of a substance.

Examples include rusting of iron or burning of wood, where new substances are formed.

Explanation

A teaching portfolio is a collection of materials like lesson plans, videos, and reflections that showcase a teacher’s skills and knowledge.

It provides direct evidence of a teacher’s competence, planning, and effectiveness in the classroom.

Explanation

A new car has been bought by him.

The sentence is in present perfect tense (has bought), so the passive form is has been bought.

"He" becomes "by him" in the passive voice, keeping the tense unchanged.

Explanation

Given the surface area of a sphere = 81π

The formula for surface area of a sphere is:

4πr² = 81π

Divide both sides by 4π:

r² = 81/4

r² = 20.25

r = √20.25

r = 4.5 m

Explanation

Given:

Hyder’s investment = Rs. 90,000

Ahsan’s investment = Rs. 60,000

Total profit = Rs. 45,000

Step 1: Find the ratio of their investments

Hyder : Ahsan = 90,000 : 60,000 = 3 : 2

Step 2: Divide the profit in the ratio 3:2

Total parts = 3 + 2 = 5

Ahsan’s share = (2/5) × 45,000 = Rs. 18,000

Explanation

Number of neutrons = Mass number − Atomic number = 19 − 9 = 10

Atomic number (9) is the number of protons; mass number (19) is protons + neutrons.

Explanation

Given log₃x = -2

This can be rewritten in exponential form:

3^(-2) = x

x = 1 / 3²

x = 1 / 9

Explanation

The suffix “-able” means capable of being or worthy of (e.g., readable = capable of being read).

It forms adjectives from verbs, indicating possibility or suitability.