Self-study
Environmentalist: Discarding old appliances can be dangerous: refrigerators contain chlorofluorocarbons; electronic circuit boards and cathode-ray tubes often contain heavy metals like lead; and old fluorescent bulbs contain mercury, another heavy metal. ████ █████████ ███ ████████ █████████ ████ █████████ ████ ██ ███████ ████████ ████ █████████ ███ ███ ████████ █████████ ████ ███ ███████ ████ ████ ███████████ ████████████ ███ ████████ ██ ███ █████ █████ ████ █████ ██ ████████████ █████ ██████ ██████ ███ ███ ███ ██████ ████ ███ ████
Summary
Discarding old appliances can be dangerous because some contain harmful heavy metals. When landfills are operated properly, the heavy metals pose no threat. When landfills are not operated properly, lead and mercury can contaminate groundwater. When trash is burned, heavy metals poison the ash and are released into the air.
Strongly Supported Conclusions
Old appliances that contain heavy metals should not be burned when discarded.
20.
The environmentalist's statements, if true, ████ ████████ ███████ █████ ███ ██ ███ █████████ ███████████
a
Old fluorescent bulbs ██████ ██ █████████
This answer is unsupported. We don’t know from the stimulus what “recycling” involves. We only know from the stimulus that old fluorescent bulbs should not be incinerated.
b
Appliances containing heavy ██████ ██████ ███ ██ ████████████
This answer is strongly supported. Since incineration causes heavy metals to poison the ash, these appliances should not be incinerated.
c
Chlorofluorocarbons are harmful ██ ███ ███████████
This answer is unsupported. We only know from the stimulus that heavy metals, when incinerated, are harmful to the atmosphere. It’s unclear from the stimulus whether chlorofluorocarbons are heavy metals.
d
Newer appliances are ████ █████████ ██ ███ ███████████ ████ █████ █████
This answer is unsupported. The stimulus is limited to older appliances. We don’t know anything about newer appliances in order to draw this comparison.
e
Appliances should be ████ ███ ██ ██████████
This answer is unsupported. The stimulus is limited to older appliances. This answer applies to appliances generally and is therefore too strong.