What should be used to create scratch orgs?

Which tag should a developer include when styling from external CSS is required in a Visualforce page?

A developer is creating an enhancement to an application that will allow people to be related to their employer. Which date model should be used to track the data?

Which action can a developer take to reduce the execution time of the following code? List<account> allaccounts = [select id from account]; list<account> allcontacts = [select id, accountid from contact]; for (account a :allaccounts){ for (contact c:allcontacts){ if(c.accountid = a.id){ //do work } } }

Which aspect of Apex programming is limited due to multitenancy?