The relational algebra expression equivalent to the following tuple calculus expression:

$$\left\{ {t|t \in r \wedge \left( {t\left[ A \right] = 10 \wedge t\left[ B \right] = 20} \right)} \right\}$$ is:

For the schedule given below, which of the following is correct:

Which of the following is correct?

Zero has two representations in: