After a Platform Event is defined in a Salesforce org, events can be published via which two mechanisms? Choose 2 answers

A Visualforce page needs to make a callout to get biding information and tax information from two different REST endpoints. The information needs to be Displayed to the user at the same time and the return value of the billing information contains the input for the tax information callout. Each endpoint might take up to two minutes to process.
How should a developer implement the callouts?

What is the transaction limit for the number of DML statements allowed?

A company has a native i0S app for placing orders that needs to connect to Salesforce to retrieve consolidated information from many different objects in a JSON format.
Which is the optimal method to implement this in Salesforce?

A Visualforce page contains an industry select list and displays a table of Accounts that have a matching value in their Industry field.

When a user changes the value in the industry select list, the table of Accounts should be automatically updated to show the Accounts associated with the selected industry.
What is the optimal way to implement this?