Explanation

The correct prepositional phrase is "in all the big hospitals" to show location.

It clearly states where the rehabilitation centers have been established.

Explanation

The sentence asks a question, beginning with "What kind of," which makes it interrogative.

Interrogative sentences are used to seek information and end with a question mark (?).

Explanation

Teaching involves direct interaction between a teacher (human) and students.

It contrasts with non-human methods like videos or software, which lack real-time human facilitation.

Explanation

To find the weighted mean:

Step 1: Calculate the weighted sum

Weighted sum = (18_2) + (19_3) + (20_4) + (21_2) + (22_1) + (23_1) + (24*1)

= 36 + 57 + 80 + 42 + 22 + 23 + 24

= 284

Step 2: Calculate the total weight

Total weight = 2 + 3 + 4 + 2 + 1 + 1 + 1

= 14

Step 3: Calculate the weighted mean

Weighted mean = Weighted sum / Total weight

= 284 / 14

= 20.286

Explanation

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

This mechanism increases torque and helps in efficient drilling.

Explanation

The number of binary relations in A × B is the number of subsets of A × B.

A has 2 elements and B has 3 elements, so A × B has 2 * 3 = 6 elements.

The number of subsets of A × B is 2^(number of elements in A × B)

= 2^6

Explanation

Allusion is a literary device that makes a brief, indirect reference to a person, event, or thing from history, literature, religion, or culture.

It assumes the reader is familiar with the reference and uses it to deepen meaning or context.

Explanation

Geometric mean is the nth root of the product of n numbers.

It is used especially in growth rates, ratios, and proportions.

Explanation

To convert degrees to radians, multiply degrees by π/180.

Formula: radians = degrees × (π/180).

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.