Explanation

The phenomenon where a chemical element exists in multiple crystalline forms is called allotropy

Allotropy refers to the ability of an element to exist in two or more different forms in the same physical state.

This is different from polymorphism, which is a broader term referring to any substance (not just elements) that can exist in multiple crystalline forms. 

Explanation

He had his breakfast at 9 o’clock.

The sentence refers to a specific time in the past ("at 9 o’clock"), so the correct tense is simple past.

"Had" is the simple past tense of "have," and it fits well with a completed past action at a specific time.

Explanation

ax² − 2x + 2a = 0  

We are told: Sum of roots = Product of roots

Step 1: Use formulas  

For a quadratic equation ax² + bx + c = 0,  

- Sum of roots = −b/a

- Product of roots = c/a

So here:  

- Sum = −(−2)/a = 2/a  

- Product = (2a)/a = 2

Set them equal:  

2/a = 2

Multiply both sides by a:  

2 = 2a  

=> a = 1

Final Answer:  

a = 1

Explanation

If matrix A is 2x3 and matrix B is 3x3, then the order of the resulting matrix AB is 2x3. 

Explanation

The additive identity of a real number is zero (0).

This means that when you add zero to any real number, the result is the original number itself.

For example, 5 + 0 = 5, and -3 + 0 = -3. 

Explanation

If matrix A has an order of 3x4, then its transpose, denoted as AT, will have an order of 4x3

Explanation

 If matrix A has an order of 3x2, then the order of its transpose (A') will be 2x3. 

Explanation

The statement "P⇒Q is true if both are true" describes a conjunction, which is the logical "and" operation.

Explanation

  A'∪B'. This is a direct application of De Morgan's Law for sets. 

Explanation

An infinite geometric series converges (has a finite sum) only if the absolute value of the common ratio, |r|, is less than 1. If |r| ≥ 1, the series diverges, meaning it does not approach a finite sum.