The correct answer is D. all of the mentioned.
EBS, iostat, and esw are all tools that can be used to measure I/O of your systems to estimate these transaction costs.
EBS stands for Elastic Block Store. It is a block storage service that provides persistent block storage volumes for use with Amazon EC2 instances. EBS volumes are highly available, durable, and scalable. They can be used to store any type of data, including application data, databases, and log files.
Iostat is a command-line tool that can be used to monitor the I/O activity of a system. It can display information about the number of I/O requests, the average I/O time, and the I/O queue length.
ESW stands for Estimated System Wait. It is a metric that is used to measure the amount of time that a system spends waiting for I/O. ESW is calculated by taking the difference between the total time that the system is busy and the total time that the system is idle.
All of these tools can be used to measure I/O of your systems to estimate these transaction costs. The best tool to use will depend on your specific needs.