Which of the following is NOT a valid variable name in JavaScript?

Which of the following will cause an error?

A). let a = 10; a = 20;

B). const a = 10; a = 20;

C). var a = 10; a = 20;

D). None of the above

What will be the output of the following code?

var a = 1; { var a = 2; } console.log(a);

A). 1

B). 2

C). undefined

D). ReferenceError

Which keyword is used to declare a variable in JavaScript?

A). var

B). let

C). const

D). All of the above

What will be the output of the following code?

console.log(a); var a = 10;

A). 10

B). undefined

C). Error

D). null

What is the difference between let and var?

A). let is function-scoped, var is block-scoped

B). let is block-scoped, var is function-scoped

C). Both are block-scoped

D). Both are function-scoped

Which of the following is true about 'const' variables in JavaScript?

A). They can be redeclared

B). They cannot be reassigned

C). They can be reassigned

D). They are always undefined

Which of the following is correct about variable scope in JavaScript?

A). var is block-scoped

B). let is function-scoped

C). const is block-scoped

D). All variables are global

What will be the output of the following code?

var x = 5; var y = 6; var z = x + y;

A). 11

B). 11

C). 5

D). 6

Which statement is true about variables in JavaScript?

A). They must be declared before use

B). They can only hold numbers

C). They are statically typed

D). They are strongly typed

Can variables declared with 'var' be redeclared in the same scope?

A). Yes

B). No

C). Only inside a function

D). Only inside a loop