Final answer:
Magnesium (D) is the element among the given options that is shiny and a good conductor of heat and electricity, which are properties typical of metals.
Step-by-step explanation:
The question asks which of the given elements is shiny and conducts heat and electricity. These are properties that describe metals. Among the options provided, magnesium (D) fits the description as it is shiny, malleable, ductile, and a good conductor of heat and electricity. Chlorine, sulfur, and hydrogen are nonmetals and do not possess these metallic characteristics. Therefore, magnesium (D) is the correct answer as it is the only metal listed and has the typical properties associated with metals.