Explanation

• Phenolphthalein is a pH indicator that changes color in response to changes in acidity or basicity.
• In an acidic medium, it is colorless, and in a basic medium, it turns pink.

Explanation

The prefix “pre-” means “before”, as seen in words like preview (before viewing) or predict (say before it happens).

It indicates something happening earlier in time or order.

Explanation

Psychology is the scientific study of behavior and mental processes (thoughts, emotions, etc.).

It explores how people think, feel, and act in different situations.

Explanation

Alliteration is the repetition of the same starting consonant sound in closely connected words.

In this phrase, the "s" sound repeats in "Silly," "snakes," "slither," and "slowly."

Explanation

In this sentence, "He's" is a contraction of "He has", showing present perfect tense.

"He has written a letter" is the full form.

Explanation

A comet grows a tail when it approaches the Sun due to the heat causing the ice to vaporize, releasing gas and dust.

This process forms a glowing coma and tail, which always points away from the Sun due to solar wind.

Explanation

Explanation

Let's solve this problem:

Initially, food is enough for 36 people for 20 days.

Total food = 36 people * 20 days = 720 people-days

When 12 more people come, the total number of people becomes:

36 + 12 = 48

Now, let's find out how many days the food will last for 48 people:

720 people-days / 48 people = 15 days

Explanation

Negative reinforcement strengthens behavior by removing an unpleasant stimulus after the desired response.

It usually follows prior conditioning, encouraging repeated behavior to avoid discomfort.

Explanation

The Concrete Level of cognitive development involves direct interaction with objects and includes attention, discrimination, mental imaging, and memory of attributes.

Recognizing and remembering a red ball fits well with this hands-on, sensory-based stage