B. Be, Mg, Ca, Sr (hope this helps)
Answer: A solution with a pH of 7 must be neutral.
Explanation:
If a solution has pH of 7 then the concentration of 
ions and 
ions will be equal.
Thus, the concentration for both ions and ions will be 
. Generally, pH at 7 is considered as neutral.
Thus, it is concluded that a solution with pH of 7 must be neutral.
You can determine the hazards of these chemicals by looking at their material data safety sheets (MSDS).
1. 0.1 M Ag⁺: Silver compounds are absorbed by skin causing bluish pigmentation. Thus, it <em>causes </em><span><em>staining on skin</em>.</span> Also, liquid <em>vapor may be irritating</em> to skin and also <em>moderately toxic when ingested</em>.
2. 0.1 M Ba²⁺: This is <em>mildly toxic when ingested</em> causing stomach irritation, muscle weakness, swelling of organs like brain, liver, kidney and heart.
3. 0.1 M Fe³⁺:Iron is <em>corrosive, has irritating vapor especially to the eyes, and toxic if ingested</em>.
4. 6 M HCl: This is a concentrated strong acid, so it is <em>corrosive, has irritating vapors, flammable and toxic when ingested</em>.
5. 6 M H₂SO₄: This is also a concentrated strong acid. Moreover, it is a strong oxidizing agent. So, its hazards include: <span><em>corrosive, has irritating vapors, toxic when ingested and causes staining on skin</em>.
</span>6. 6 M HNO₃: This is a concentrated strong acid, so it is <em>corrosive, has irritating vapors, flammable and toxic when ingested</em>.
7. 7.5 M NH₃: This is a weak base. It is characterized for its pungent odor. This is <em>corrosive, has irritating vapors, toxic if ingested, and flammable</em>.
Carbon Dioxide is used in celular respiration. All other choices are waste products
