All of the halogens a. exhibit metallic character b. form salts with alkali metals with the formula mx c. exist under ambient conditions as diatomic gases d. tend to form negative ions of several different charges e. tend to form positive ions of several different charges

Let's examine the choices we have:
A is wrong since halogens are non-metals
B is correct as halogens reacts with metals to form salts. Example of this is the reaction of sodium with chlorine to form sodium chloride
C is not completely right since I2 is liquid under ambient conditions and not gaseous.
D is wrong as they form negative ions of only -1 charges
E is wrong since they non-metals so they tend to form negative ions.

Based on this:
The right choice is: b. form salts with alkali metals with the formula mx 

Less stable  hope this

The answer is nitrogen-containing bases