15.下列各式中,最简二次根式是( )
0 284569 284577 284583 284587 284593 284595 284599 284605 284607 284613 284619 284623 284625 284629 284635 284637 284643 284647 284649 284653 284655 284659 284661 284663 284664 284665 284667 284668 284669 284671 284673 284677 284679 284683 284685 284689 284695 284697 284703 284707 284709 284713 284719 284725 284727 284733 284737 284739 284745 284749 284755 284763 366461
| A. | $\sqrt{0.3}$ | B. | $\sqrt{12}$ | C. | $\sqrt{6{x}^{3}}$ | D. | $\sqrt{{x}^{2}+1}$ |