Due to provider requirements, outgoing calls from the Enterprise to the PSTN must start with channel 1. Which ISDN command changes the channel selection on IOS to meet this requirement?

The `isdn bchan-number-order ascending` command forces the router to select B-channels in increasing order, meaning channel 1 will be used first for outgoing calls if available. This directly addresses the provider requirement for outgoing calls to start with channel 1. This configuration is applied to the ISDN interface for channel selection behavior.

The `isdn protocol-emulate network` command configures the ISDN interface to emulate a network device, typically used for testing or specific interoperability, not for channel selection order.

The `isdn incoming-voice` command specifies that the ISDN interface should process incoming calls as voice calls, not controlling the outgoing channel selection order.

The `isdn bchan-number-order decending` command would cause the router to select B-channels in decreasing order, starting from the highest available channel, which contradicts the requirement to start with channel 1.