bcz the defination of matter is that
anything which occupy space
- water can occupy space so it is matter
- fact :something that you know has happened or is true which doesn't occupy any space so this option is false
- energy : energy is the quantitative property that must be transferred to a body or physical system to perform work on the body, or to heat it. it doesn't occupy any space so this option is false
- A theory is a well-substantiated explanation of an aspect of the natural world that can incorporate laws, hypotheses and facts.--it doesn't occupy any space so this option is false
Hence , option a is correct