[填空题]Dung fossils are often found in rocks that have been worn down by ______.

[填空题]Dung fossils are often found in rocks that have been worn down by ______.

[单项选择]Rocks which have solidified directly from
molten materials are called igneous rocks.
Igneous rocks are commonly referred to as
Line primary rocks because they are the original
(5) source of material found in sedimentaries and
metamorphics. Igneous rocks compose the greater
part of the earth’s crust, but they are generally
covered at the surface by a relatively thin layer of
sedimentary or metamorphic rocks. Igneous rocks
(10) are distinguished by the following characteristics:
(1) they contain no fossils; (2) they have no regu-
lar arrangement of layers; and (3) they are nearly
always made up of crystals.
Sedimentary rocks are composed largely of
(15) minute fragments derived from the disintegration
of existing rocks and in some instances from the
remains of animals. As sediments are transported,
individual fragments
A. differentiate between and characterize igneous and sedimentary rocks
B. explain the factors that may cause rocks to change in form
C. show how the scientific names of rocks reflect the rocks’ composition
D. define and describe several diverse kinds of rocks
E. (E) explain why rocks are basic parts of the earth’s structure

[单项选择]