Converting Unique,Filter,Countif formula in Google Sheets to Excel

Hi,
I have a list of students (by ID#) with Ds,D+, and Fs. I need a formula to organize them into 3 categories: Only 1 D or D+, >1D or D+, 1 or more Fs. Students can only be in one of the categories and I need their student ID returned.
Since I work mostly in Google Sheets, I was able to get the right formulas but for security reasons I need to move it over to Excel. And I just realized Excel and Sheets formulas are not all from the same world.

Any help would be much appreciated!

attaching a sample

Thanks, those formulas do seem to work perfectly. Question though: when I tried to adjust the formula to include more rows, it stopped working and just gave me a blank (even after I used ctrl+shift+enter). I'm going to use this spreadsheet as a template for a few teachers to enter data of unknown varying sizes. I want the formula to work say to row 1000 to cover all possibilities. How can I do that?

For instance in C2 I tried:
=IFERROR(SMALL(IF(FREQUENCY(IF(LEFT($B$2:$B$100)="D",$A$2:$A$100),$A$2:$A$100)=1,$A$2:$A$100),ROWS(C$2:C2)),"")

Which just changed all row 11's to row 100, but that didn't seem to work.