The instrument used for measuring the humidity of air is a :

1) Which is true regarding actual air temperature and dewpoint temperature spread? The temperature spread:

2) Throughout the 24hrs of a day the relative humidity can be expected to :

3) During a night with a clear sky, surface temperature will ---------- RH will --------- and dewpoint will ----------

4) A change of state directly from a solid to a vapor or vice versa is :

5) The instrument used for measuring the humidity of air is a :