Which step in external respiration allows O2 to move from the external environment to the alveolar spaces

Need will mark ! which features are created by groundwater erosion and deposition? check all that apply. a. stalagmitesb. sinkholesc. rillsd. stalactites e. gullies f. rivers

According to piaget, children have acquired the cognitive skill of conservation when they're able to a. understand that six ounces of liquid in a jar and six ounces in an elongated tube are equal. b. understand the viewpoint of other people. c. relate objects around them to their own needs. d. realize that the term heavy describes an object one way and the term big describes it another way. it is not b nor c. did this 2 x wrong..

How many species of living things are alive on earth today? more than 1,000,000 none of these answers are correct 100-500 1,000 –500,000 o 500,000 -1,000,000