If you could change any part of the cross-training challenge, what would you change? Why?

Efficiency is an action of doing something. for example when you take a test. good efficiency means you did well but bad effeciency or no effiency means you did bad.

It won't lose or gain electrons if it's a covalent bond it shares the electrons with another atom or atoms. if it is an ionic bond it will lose the 3 electrons on the outer shell and become a positively charged ion.  credit goes to @sunshinebaby of answers.yahoo.com.

answer and explanation;

composition refers to both the types of minerals within a rock and the overall chemical makeup of the rock while texture refers to the size and arrangement of the minerals or grains that make up a rock. both composition and texture can be used to classify rocks, such as igneous rocks. texture describes how the rock became solid or crystallized from liquid, melted rock. composition of a rock describes the minerals that make up a particular rock.