The correct answer to this question is A, In series. There are two ways that a battery can be connected. The first is in series. This involves doubling the voltage. While it is doubled, the same capacity rating is maintained.
Examples, where this type of connection would be used, include scooters and vehicles for kids. The other connection is in parallel. Here, the capacity is still doubled, but the voltage of only one of the batteries is maintained.
An example where this type would be used would include in batteries for laptops. Some scooters also use parallel connections. Each connection has its own way that the connection is made.