Refer to the show spanning-tree mst configuration output .

What should be changed in the configuration of the switch SW_2 in order for it to participate in the same MST region?

A.
Switch SW_2 must be configured with the revision number of 2.

B.
Switch SW_2 must be configured with a different VLAN range.

C.
Switch SW_2 must be configured with the revision number of 1.

D.
Switch SW_2 must be configured with a different MST name.

Explanation:

MST is built on the concept of mapping one or more VLANs to a single STP instance.
Multiple
instances of STP can be used (hence the name MST), with each instance supporting a different
group of VLANs.

In most networks, a single MST region is sufficient, although you can configure more than one
region. Within the region, all switches must run the instance of MST that is defined by the following
attributes:
MST configuration name (32 characters)
MST configuration revision number (0 to 65535)
MST instance-to-VLAN mapping table (4096 entries) Example of configuration of MST

Switch(config)# spanning-tree mode mst
Switch(config)# spanning-tree mst configuration
Switch(config-mst)# name name
Switch(config-mst)# revision version
The configuration revision number gives you a means to track changes to the MST region configuration. Each time you make changes to the configuration, you should increase the number by one. Remember that the region configuration (including the revision number) must match on all switches in the region. Therefore, you also need to update the revision numbers on the other switches to match.
Switch(config-mst)# instance instance-id vlan vlan-list The instance-id (0 to 15) carries topology information for the VLANs listed in vlan-list. The list can contain one or more VLANs separated by commas. You can also add a range of VLANs to the list by separating numbers with a hyphen. VLAN numbers can range from 1 to 4094. (Remember that by default, all VLANs are mapped to instance 0, the IST.) Switch(config-mst)# show pending
region configuration:
Switch(config-mst)# exit

So belong the routers in same MST region, MST attributes should be same, in SW_2 router revision number is not same so to make belong the SW_2 router on same MST region, revision number should be 1.