FULLY SWITCHED STP (Spanning Tree Control)

The Spanning Tree Protocol (STP) is a network protocol which makes certain a loop-free topology for just about any bridged Ethernet LAN (local area network). The fundamental purpose of STP would be to avoid bridge loops and also the broadcast radiation which will result from them. Spanning tree additionally enables a network design to incorporate extra (redundant) links to offer automated back-up routes in the event that an active link does not work out, with no risk of bridge loops, or perhaps the requirement for manual enabling/disabling of those backuplinks.
Advantages:

Verified and also broad assistance by bridges and switches

Simple to implement
Disadvantages:

Not really ideal utilization of network infrastructure (links in back-up mode aren't utilized for forwarding)

RB signifies a SPoF (Single Point of Failure)

Almost all traffic undergoes RB (therefore could become a logjam)

Sluggish convergence in the event of topology modifications (set with RTSP)
I would choose a STP (in a fully switched environment) for the following reasons:

The purpose of the spanning tree protocol (STP) is to identify and temporarily block the loops in a VLAN or network segment.


The switches run the STP, which involves electing a root bridge or switch. The other switches measure their distance from the root switch. If there is more than one way to get to the root switch, there is a loop. The switches follow the algorithm to determine which ports must be blocked in order to break the loop.

STP is dynamic; if a link in the segment does not work out, ports that were originally blocking can possibly be changed to forwarding mode.

Newer methods such as SPB (Shortest Path Bridging, IEEE 802.1aq) or TRILL
(RFC6325) enable making use of all links therefore enhancing network usage whilst offering functions such as balancing and load distribution.
From the above network diagram, I feel that Switch-A should serve as the route switch and
Switch-B as the back-up root switch because A serves both the switches A and B along with the main server and B best serves as a back-up root as it is near to the broadcast tower.
To ensure rapid convergence,
Almost all ports specifically linked to end stations are not able to generate bridging loops within the network. Consequently, the edge port immediately changes to the forwarding state, and also skips the actual listening as well as learning phases. Within switched networks these days, many links run in full-duplex mode and they are handled like point-to-point links by means of RSTP. This will make them prospects with regard to rapid transition towards the forwarding state.

References:

Perlman, Radia (2000). Interconnections, Second Edition . USA: Addison-Wesley.