1. alginate is
a. reversible hydrocolloid impression material
b. irreversible hydrocolloid impression material
c. polysulfideimpression material
d. polyvinyl siloxane impression material

Option b, Irreversible hydrocolloid impression material

Explanation:

Irreversible is used as an impression material to take impression from edentulous jaws. It is also used in wound healing and drug delivery.

Alginate is a natural polymer found in cell wall of brown seaweed.

Its monomers are β-D-mannuronate and α-L-guluronate.

In association with Ca2+, it forms gel. It is hydrophilic in nature.

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

if it's not useful, feel free to report for mistake in answer.