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The question is about "What is the largest composite number less than 30".
Before starting let us see what is the composite number?
"A number that can be divided exactly by numbers other than 1 or itself is called a composite number".
So according to the defination of composite number are 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, ...
Now the question is what is the largest composite number less than 30 ? And given four option are 23,25,28,29.
Here 30 will not be included because we need less then 30.
Here 29 also will not be included because 19 is not composite number it is a prime number.
Here 28 is divisible by 2. Its mean it has more then 2 factor. So 28 is less then composite number and it is also less then 30. So 18 is the required composite number.
Here 25 is divisible by 5. It is composite number.
Here 23 is not divisible by any number. So 23 is prime number.
So final answer is 28 is the required composite number which is also less then 30.