Answer:
The formula will change to =SUM($A10:E10)
Step-by-step explanation:
Look at the difference between =SUM($A1:C1) and =SUM($A10:E10).
In both cases column A is present because in the original formula 'A' is next to '$' sign.
In the original formula the row 1 is used because the destination cell, D1, is in row 1; after the copy is made, the destination cell F10 is in row 10, so the '1' is changed to a '10'.
C is changed to E because C column is the previous column to the destination cell, D1, in the original formula and E is the previous column to the destination cell, F10, after the copy.