Question

a cup of coffee is an example of an open system. it allows matter to leave. it heat energy ______ to leave

Explanation:

In thermodynamics (a subfield of Physics, under Natural Science), an open system allows both matter and energy (including heat energy) to transfer in or out. A cup of coffee as an open system allows heat energy "also" to leave (since it allows matter to leave and heat energy transfer is also possible in open systems; the blank likely needs "also" to complete the sentence logically, fitting the context of open system properties).

Answer:

also