My friend and I are struggling with this question from our English textbook:
Choose the best sentence that can be made from the words given:
we / dependent / nature / cannot survive ourselves / without wildlife
a. As we are dependent on nature and we cannot survive ourselves without wildlife.
b. We dependent on nature and therefore cannot survive ourselves without wildlife.
c. We are dependent on nature and so cannot survive ourselves without wildlife.
d. We are dependent on nature and cannot survive ourselves without wildlife.
We can clearly see grammatical mistakes in a. and b., but we are not sure if both c. and d. are correct. Or is the textbook wrong?