A.
sql = sql + "and ([BookAuthor] LIKE '%" + TextBoxAuthor.Text + "%')";
B.
sql = sql + "and ([BookDisCount] <= '" + (DropDownListDisCuount.SelectedValue).ToString() + "' )"
C.
sql = sql + "and ([BookName] LIKE '%" + TextBoxBookName.Text + "%')";
D.
sql = sql + "and ([BookPublisher] LIKE '%" + TextBoxPublisher.Text + "%')"