Back to the 1M row data sheet. 
We can find out how many different values there are in a column.
 Copy the three text columns (B, D, and F) to a new sheet. 
 On that sheet, in Data tab,  Remove Duplicates of each column by itself. 
  (choose "Continue with current selection")
 How many unique values are there of column B:________
 How many unique values are there of column D:________
 How many unique values are there of column F:________
 Sort each column to see that there are no duplicates.
  (choose "Continue with current selection")
  What's the first 6-letter word:_________, the last:__________
  What's the first 4-letter word:_________, the last:__________
  How many different 6-letter words are there that start with 'to':_______
  (hint: apply a Filter to this column, "Begins with")
Copy column A's million values to this new sheet. Remove its duplicates.
 How many duplicates are there in column A:_________
Delete this sheet after you've done the above.