You Deploy and Exchange organization. All Servers in the organization have Exchange
Server 2010 SP1 installed. The organization contains two Hub Transport servers.
The network contains two Active Directory sites named site1 and site2. Each site contains
one hub transport server. Each site has a direct connection to the internet.
You need to configure message routing for the organization to meet the following
requirements:
E-mail messages to a SMTP domain named nwtrader.com must be delivered from site2.
IF site2 is unavailable, e-mail messages sent to nwtraders.com must be delivered from site1.
E-mail messages sent to all other SMTP domains must be delivered from site1 only.

What should you do?

A.
Create two Send connectors.
Assign one Hub Transport server as a source server to each Send connector.
Configure the connectors as Scoped send connectors.

B.
Create one Send connector.
Assign both Hub Transport servers as source servers.
Configure the connector as a Scoper send connector.

C.
Create one Send connector.
Assign both Hub Transport servers as source servers.
Configure the address spaces for the connector, and then configure the costs for the
address spaces.

D.
Create two Send connectors.
Assign one Hub Transport server as the source server to each Send connector.
Configure the address spaces for each connector.

Explanation:
You already know from the question you need 2 send connectors, this rules out 2 answers.
No need for a Scoped send connector so leaves only 1 answer.

http://technet.microsoft.com/en-us/library/aa998662.aspx