A:Fe→点燃Cl2FeCl2→NaOH(aq)Fe(OH)2
B:S→点燃O2SO3→H2OH2SO4
C:CaCO3→高温CaO→高温SiO2CaSiO3
D:NH3→催化剂,△O2NO→H2OHNO3
—________?
— He's swimming at the pool.
某物体发出的声音在空气中的波长为1 m,波速为340 m/s,在海水中的波长为4.5 m,此物体在海面上发出的声音经0.5 s听到回声,则海水深为____ m.