To remove a Grid, select all columns in the Grid then click Row/Col, Remove. (Easy ways to select all colums: (1) drag your mouse in a horizontal line from the leftmost column to rightmost column, selecting a whole row; (2) click in the leftmost cell and shift-click in the rightmost cell.)
To remove a Q&A Table and any Grids that follow it, select all rows in the Q&A table then click Row/Col, Remove. (Easy ways to select all rows: (1) drag your mouse in a vertical line from the first answer to last answer; (2) click in the first answer and shift-click in the last answer.)