On which of the following assumptions is based the belief, that tree-ring thicknesses show links between solar periodicity and terrestrial climate?
A.
Solar-activity cycle existed m its present form. during the period in question.
B.
Average tree-ring thickness varies from species to species.
C.
Tree-ring thickness varies with changes in terrestrial climate.
D.
Both terrestrial climate and solar-activity cycle randomly affect tree-ring thickness.