Wap to read a postitive sentence. Convert and display its negative sentence

Question

input: this is my bike
output: this is not my bike

Can anyone code this in C# using string?
am a beginner in C#

Answer 1

I think it can't be done easily, since there are different types of sentences...
for a sentence like one above you can find the index of 'is' and replace it with 'is not'
may be a solution. But in other case

for a sentence,
I am Vishnu
you should check position of 'am'

and for every different cases different conditions will be there to check