Throwing Exceptions in Apex:
throw new ExceptionType();creates a new instance and throws it.
A: No argument constructor.
B: Constructor with a custom error message.
Why Not Other Options?
C and D: These create exception instances but do not throw them, which is not valid syntax for firing an exception.
References:Apex Exception Handling:https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta
/apexcode/apex_classes_exception_methods.htm

When using SalesforceDX, a developer needs to enable Dev Hub in order to create and manage scratch orgs. A Dev Hub is a special type of org used by developers to store source code and other development-related artifacts. It is also used to create and manage scratch orgs, which are temporary orgs used for development and testing.
Reference: https://developer.salesforce.com/docs/atlas.en-
us.sfdx_dev.meta/sfdx_dev/sfdx_dev_intro.htm

sObject:SOQL queries can return single or multiple records assObjectinstances.
List:SOQL queries often return results as aListofsObject.
Double:SOQL aggregate queries can return numeric data types likeDouble(e.g., COUNT, SUM).
Reference:SOQL Query Return Types
Incorrect Options:
B (Long):SOQL does not directly returnLongvalues.
D (Integer):Aggregate results useDouble, notInteger