Some studies suggest that babies placed in full-time child care before 3-5 years of age are more likely to display insecure attachment in the strange situation. <span>Attachment is the emotional bond between the child and the parent. Hope this answers the question.</span>
        
             
        
        
        
Answer: Density Dependent Limitation
Explanation: Limitations to population growth are either density-dependent or density-independent. Density-dependent factors include disease, competition, and predation.
 
        
             
        
        
        
Increasing the cell's volume would reduce the efficiency of the diffusion of materials through the plasma membrane into the cytoplasm of the cell. 
On the other hand, increase the surface area and decreasing the volume oft the cell would increase the rate of diffusion across the plasma membrane.
        
             
        
        
        
Answer:
Control group: volunteer stationary bike riders in a pollution-free chamber
Experimental group: volunteer stationary bike riders in a chamber filled with air pollutants common to Los Angeles
Independent variable: exposure to air pollution
Dependent variable: The heart rates (physical fitness) of the volunteer riders.
Explanation:
In a scientific experiment, data is compared between the control group and experimental group to ascertain the effect of the independent variable on the dependent variable. A control group is the group in an experiment that is not treated with the independent variable i.e. the independent variable is controlled while the experimental group is the group that is treated with an independent variable. 
N.B: The independent variable is the variable controlled by the experimenter in order to influence the dependent variable (measurable outcome).
In this experiment, the independent variable is the AIR POLLUTION the volunteer riders are exposed to while the dependent variable is the PHYSICAL FITNESS/ HEART RATES of the volunteer riders, which is dependent on the exposure to air pollution (independent variable). 
The control group in this experiment is the volunteer riders placed in a POLLUTION-FREE CHAMBER where the independent variable cannot influence or have any effect on the measurable variable (dependent). The experimental group is the volunteer riders placed in a CHAMBER FILLED WITH AIR POLLUTANTS. The independent variable (air pollution) has been changed in the experimental group.