Elastic Beanstalk environment has been used for your team recently for a feature development based on Java. When the team firstly created the environment, they were using a single instance as they did not consider the capacity. However, after a while you find that the application needs to consume more memory and CPU than being expected sometimes during traffic spike. As a result, the application has some performance issues. Your AWS solution architect suggests you use multiple instances rather than one. What should you do?

Answer options:

A.Change your environment type to a high available environment by editing your environment`s configuration. In the Elastic Beanstalk console, select the environment, add multiple instances with autoscaling based on MemoryUtilization.
B.Destroy the environment. Create a new environment type that has multiple instances as your old environment cannot be modified to a multiple instances environment.
C.Modify the environment`s capacity settings to a load balanced environment type with autoscaling. Select all availability zones. Also add a scaling trigger if average CPUUtilization is over 85% for a 5 minutes period.
D.Edit your environment`s capacity configuration to a load balanced environment type. Make sure that all availability zones are selected. Add a scaling event when median CPUUtilization is over 85% for a period of 1 minute.
E.Modify the instance type to t2.large to meet the need of high CPU and memory.

Option C is Correct:
In AWS Elastic Beanstalk, you can create a load-balancing, autoscaling environment or a single-instance environment. The type of environment that you require depends on the application that you deploy. For example, you can develop and test an application in a single-instance environment to save costs and then upgrade that environment to a load-balancing, autoscaling environment when the application is ready for production.
For more information, refer to
https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/using-features-managing-env-types.html
To use Amazon EC2 Auto Scaling effectively, configure triggers that are appropriate for your application, instance type, and service requirements. You can scale based on several statistics including latency, disk I/O, CPU utilization, and request count. Refer to
https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/environments-cfg-autoscaling-triggers.html
for the Elastic Beanstalk AutoScaling triggers.
Option A is incorrect because MemoryUtilization is NOT a scaling trigger for Elastic Beanstalk multi instances environment. The valid triggers include CPUUtilization, NetworkIn, Latency, DiskReadOps, etc.
Option B is incorrect because you do not need to destroy this existing one to change the environment type.
Option D is incorrect because the valid statistics for scaling trigger are Max, Mim, Sum and average. Median is not a valid one. Refer to the below:
Option E is incorrect: because you are unsure if t2.large instance type is able to meet the need. Also the traffic is not stable so that a higher capacity instance type is not cost effective. The best solution is to use the auto scaling environment that Elastic Beanstalk provides.