Indicate whether the following statements are True (T) or False (F).
1. The difference of two real numbers is always a real number.
2. The quotient of two real numbers is always a real number (provided the denominator is non-zero).
3. The sum of two real numbers is always a real number.
4. The ratio of two real numbers is never zero.
5. The difference of two real numbers is always an irrational number.
6. The quotient of two real numbers is always a rational number (provided the denominator is non-zero).
7. The product of two real numbers is always a real number.