Which of the following is not a factor of production(this is an economics class question)

a. the land required for a hog farm

b. the training required to repair an airplane engine

c. the teacher required to teach an economics class

d. the amount of money required to buy a car

uses : -

1.aneroid barometers primarily measure whether pressure is rising or falling.

2.aneroid barometers are often used for reading pressure in homes and recreational boats.  

3.other uses may include barographs in meteorology and altimeters in modern aircraft.  

4.this type of barometer can announce whether a high or low pressure system is coming or whether it is becoming more intense.  

5.there are different types of aneroid barometers, such as the altimeter, which measures altitude, or distance above sea level.  

6.another example is a barograph, which is a modified aneroid barometer that provides constant readings of atmospheric pressure on graph paper.  

7.when used in this capacity, the aneroid barometer can store a week's worth of data.

android diameter a device for measuring atmospheric pressure , often specially calibrated for use as an altimeter ,consisting of a box or chamber partially exhaused of air, having an elastic top and a pointer to indicate the degree of compression of the top caused by the external air

refer to the attachment for the characteristics : -

answer; i believe the correct answer is (8) eight.