What causes a valley to become shallow or deep?

What is the approximate chemical composition of the solar nebula?

What effect has the drug trade had on some governments in middle and south america? a. it has funded political instability. b. many nations have created democratic governments. c. many governments have allowed the drug trade to fund local programs. d. it has funded political stability.

According to the article about the zhou dynasty, this dynasty was broken into different eras because its capital changed from place to place. how many different eras were there in the zhou dynasty? a. two b. six c. ten d. fourteen