For which of the following is there an induced emf?

1. A conducting rod is pulled on conducting
   rails that are placed in a uniform magnetic field directed into the
   page.
2. A conducting loop moves through a uniform magnetic field
   directed into the page.
3. A conducting loop rotates in a uniform
   magnetic field directed into the page.
4. A conducting loop moves
   in a magnetic field produced by an infinite current-carrying wire.

1. A only
2. A and B only
3. A and C only
4. A and D only
5. B and C only
6. A, B, and C
7. A, C, and D
8. All of them
9. None of the above