This is a cell, which is the basic unit of all life. all organs in human bodies are made of cells and require oxygen to survive. which two systems work together to deliver oxygen to cells throughout the body?
a) skeletal and endocrine
b) digestive and endocrine
c) skeletal and respiratory
d) respiratory and cardiovascular

The force acting on a beam was measured under the same operating conditions and a sample of 5 data points was collected. this process was repeated by 3 observers. the pooled standard deviations of these 3 data sets was 1.21. determine the true mean force using all pooled data (with a 95% probability). the result should look like this: true mean = mean +/- margin of error