Answer:
evolution of bidepadlism,
increase in enamel thickness,
regular use of stone tools, enlargement of brain to around 1,450 cc
Explanation:
I believe it is d
It contains partial positive and negative charges.
A hydrogen bond is a non-covalent bond between a partial negative charge and a partial positive charge. Hydrogen bonds tend to be weak. Hydrogen bonds tend to be transient.
a or d
C
c. Cells contain tiny organisms within them.