For a cloud to form, water vapour must condense. This happens when the temperature reaches its dew point. Consequently, for a cloud to form the temperature and dew point lines on a tephigram must meet. If this happens at the surface, the cloud formed there is commonly called mist or fog. If it happens above the surface, the name of the cloud will vary but in the first 6000 will be either stratus or cumulus depending on the stability of the layer.
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Refer to the image. Which tephigram represents the conditions for low stratus?