Can I use VeraCrypt to encrypt both drives in my laptop?

This is indeed possible. Check out the documentation of Favorite Volumes and System Favorite Volumes.

It sounds like you want System Favorite Volumes that will decrypt the D: drive upon bootup. Please note, this requires both drives to have the same password. Here are the links to the detailed documentation.

https://www.veracrypt.fr/en/System%20Favorite%20Volumes.html

https://www.veracrypt.fr/en/Favorite%20Volumes.html

Here is how you make a volume a system favorite:

1. Mount the volume (to the drive letter to which you want it to be mounted every time).

2. Right-click the mounted volume in the drive list in the main VeraCrypt window and select ‘Add to System Favorites’.

3. The System Favorites Organizer window should appear now. In this window, enable the option ‘Mount system favorite volumes when Windows starts’ and click OK.