The boundary where crust gives way to mantle is called the
a. asthenosphere
b. mesosphere
c. mohorovicic discontinuity
d. vernian divide

chemical weathering is the breakdown of rocks, soils, and minerals through
a. atmospheric or biologically produced chemicals
b. atmospheric conditions
c. the movement of wind and water
d. mechanical means

the cracking of rock due to heat is an example of
a. erosion
b. physical

1. The boundary where crust gives way to mantle is called the Mohorovicic discontinuity. The correct option in regards to the given question is option "c".
2. Chemical weathering is the breakdown of rocks, soils and minerals through atmospheric or biologically produced chemicals. The correct option in regards to the question is option "a".
3. The cracking of rock due to heat is an example of physical weathering. The second option or option "b" is the correct option in regards to this question.
I hope to have correctly answered all the questions you posted.