室温下，下列各组离子在指定溶液中能大量共存的是

A．含有大量NO^—₂的水溶液中：Na⁺、Fe²⁺、SO^2-₄、H⁺

B．在pH=12的溶液中：ClO^—、S^2-、Na⁺、K⁺

C．能使pH试纸变蓝的溶液 NH₄⁺Na⁺SO₄^2－Fe^3＋

D．含有大量HCO^—₃的澄清透明溶液中：K⁺、C₆H₅O^—、Cl^—、CH₃COO^—

____ will he be back? In a week.　[ ]

A. How long

B. How soon

C. How often

D. How many