Which technique can run logic when an Aura Component is loaded?

A developer is writing unit tests for the following method: public static Boolean isFreezing(String celsiusTemp) { if(String.isNotBlank(celsiusTemp) && celsiusTemp.isNumeric()) return Decimal.valueof(celsiusTemp) <= 0; return null; } Which assertion would be used in a negative test case?

Given a list of Opportunity records named opportunityList, which code snippet is best for querying all Contacts of the Opportunity's Account?
A)

B)

C)

D)

A developer has created a Visualforce page that uses a third-party JavaScript framework. The developer has decided to supply data to the JavaScript functions using JavaScript Remoting for Apex Controllers.
What is the correct syntax to declare a remote method in Apex? (Choose two.)

A company has a native iOS 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?