The correct answer is D. all of the mentioned.
Cloud computing vendors run very reliable networks. This is because they have a large number of servers that are located in different geographical locations. This means that if one server goes down, there are other servers that can take over. Additionally, cloud computing vendors have a team of experts who are constantly monitoring the network and making sure that it is running smoothly.
The low barrier to entry cannot be accompanied by a low barrier to provisioning. This is because if the barrier to entry is low, then anyone can start a cloud computing company. However, if the barrier to provisioning is low, then it will be easy for customers to switch to another cloud computing company. This would make it difficult for cloud computing companies to make a profit.
A. except for tightly managed SaaS cloud providers is not correct. This is because even tightly managed SaaS cloud providers run very reliable networks.
B. cloud computing vendors run very reliable networks is correct. This has been explained above.
C. the low barrier to entry cannot be accompanied by a low barrier to provisioning is correct. This has been explained above.
Therefore, the correct answer is D. all of the mentioned.