Dr. prentice, principal of an elementary school, instructs her teachers to employ a new aggression-reduction program with the second graders and to keep using it on that group of students for the next three years. she finds that, relative to the start of the program, aggression in that group of students is down 35%. this example illustrates the possibility of as a plausible rival hypothesis.

The answer is maturity.

Explanation:

In the example, the age difference might be the cause for the changes in attitude, as it was performed over the course of three years (and thus it's difficult to test the validity of the program itself).

In fact, some studies have shown that less psychologically mature teenagers tend to present more aggresive behaviours. However, not much further research has been done.

answer; /// i believe that the correct answer is (a) making presentations;

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 : -