Explanation
The easiest method to change the work hours information in the Salesforce org to reflect the new time zone is to go to Settings -> Personal Information -> My Work Information, and select the appropriate time zone from the drop-down menu.

Selecting Fields to Display is what the associate should do to add the missing key columns to the custom Contact list view. Selecting Fields to Display is a feature that allows the user to choose which fields to show as columns in the list view, and in what order. The user can select up to 15 fields to display, and drag and drop the fields to rearrange the column order. Editing list filters is a feature that allows the user to apply one or more criteria to filter the records that are displayed in the list view. The user can select a field, an operator, and a value for each filter, and combine multiple filters with AND or OR logic. Editing sharing settings is a feature that allows the user to control the access and visibility of records for different users and groups. The user can define the organization-wide default, role hierarchy, sharing rules, and manual sharing for each object.

Explanation
Creating a dashboard is the recommended way to meet the requirements of displaying an easy-to-understand visual representation of accounts and opportunities that have been worked on by the sales agents in the current quarter. A dashboard is a collection of components that display data from one or more reports in a graphical format, such as charts, gauges, metrics, and tables. A dashboard allows the user to identify trends, sort data, and measure the impact of their activities. For example, a dashboard could show the number of accounts and opportunities by sales agent, the total amount of closed won opportunities by month, and the average deal size by industry. Creating a list view would not work, because a list view is a filtered set of records that display data in a tabular format, not a graphical format. A list view does not allow the user to identify trends, sort data, or measure the impact of their activities. Creating a custom tab would not work, because a custom tab is a user interface element that allows the user to access a custom object, a web page, or a Lightning page. A custom tab does not display data in a graphical format, but in a record detail or page layout format.