A system .

(A) is a fixed amount of matter and a control volume
(B) is a volume in space.
(C) is a volume in space and a control volume is a fixed amount of matter.
(D) and a control volume are both a fixed amount of matter.
(E) and a control volume are both a volume in space.

(B) is a volume in space.

Explanation:

A system is the space chosen form the universe for the study and analysis.

There are 3 kinds of systems :

1) Open system:

This system can interact to surroundings in terms of both mass and energy transfer through its boundaries.

2) Closed system:

This type of system can only interact to the surrounding in terms of energy transfer through its boundary.

3) Isolated system:

This type of system cannot interact with the surrounding by any means and its energy remains constant with time under the observation.

It has insulated boundary.

specific latent heat of fusion, lf, of a substance is defined as the amount of heat required to change a unit mass of the substance from solid to liquid state, without any change in the temperature.

explanation: