In a bread recipe, the amount of flour specified should be a non-negative number, as you cannot use a negative amount of an ingredient. Therefore, among the given options:
- Negative 3: Not valid (negative)
- Square root of 3: Positive but not a whole number, so it could be used in a recipe but might be less practical.
- 2 3/4: Valid (positive and can be used as a measurement in cups)
- 4/7: Valid (positive and can be used as a measurement in cups)
The numbers that could be used to specify how many cups of flour should be used are 2 3/4 and 4/7.