Indicate whether the following statements are True (T) or False (F).
1. The difference of two rational numbers is always a rational number.
2. The quotient of two rational numbers is always a real number (provided the denominator is non-zero).
3. The sum of two rational numbers is always a rational number.
4. The ratio of two rational numbers is always positive
5. The difference of two rational numbers is always a natural number.
6. The quotient of two rational numbers is always a rational number (provided the denominator is non-zero).
7. The product of two rational numbers is always a rational number.