The current population of the United States of America is 325,372,521 as of Thursday, January 12, 2017, based on the latest United Nations estimates.
Mountains such as the rocky mountains
B. Natural selection and Evolution both show the change over time in the survival of a specific organism. Natural Selection chooses traits that correspond the best with the ecosystem, while evolution gradually changes the species as a whole to cope with the surroundings.
Answer:
I don't think it was because your room wasn't clean. The main cause of bed bugs is travel, which means most likely you got one on you when you went outside or something, and you accidentally got it into your room. Bed bugs hitchhike on luggage, clothing, people, etc.
If there are blood stains or dark/rusty spots on your bed/pillow, there are definitely bed bugs. The bloodstains/spots come from you crushing the bed bugs accidentally. The place where bed bugs are (in this case, your room), may also begin to smell bad. You might also see eggs laid by the bed bugs.
Let me know if you have any other questions. Good luck!