To query child records from a parent object, you need to use a subquery inside parentheses. The subquery should specify the fields to retrieve from the child object, and the relationship name to use. The parent object should be specified after the FROM clause, and any filter conditions on the parent object should be specified after the WHERE clause. In this case, the parent object is Contact, the child object is Job_Application__c, the relationship name is Job_Applications__r, and the filter condition is Account.Industry = 'Technology'.
The other options are incorrect because they use the wrong relationship name or syntax. Option B uses Accounts instead of Account, which is not a valid field on the Contact object. Option C uses Job_Applications_c instead of Job_Applications__r, which is not a valid relationship name. Option D uses Job_Application_c instead of Job_Applications__r, which is also not a valid relationship name. References:
* Trailhead: Write SOQL Queries
* Trailhead: Querying Data with SOQL
* Salesforce Developer Guide: Relationship Queries