(A) Nominal measure gives a name with no numerical indication. Ordinal ranks the list, but the ranking has no numerical indication (e.g. Blue ribbon, red ribbon or first/second place). Interval data is numerical but has no true zero. Finally, ratio level is numerical with a true zero and the ratio of pieces of data reflects the true proportion.
Temperature is interval. There is no true zero (a negative temperature is not a lack of any heat) and `60^@` is not twice as warm as `30^@` .
(B) Gender is qualitative -- there is no number attached.
(C) I don't know what your line of work is. Discrete variables are countable -- e.g. there is a definite number of items. For instance the number of people who visit your store is discrete -- it is not possible to have 181.5 people enter your store.
A continuous variable is often measurable. The amount of gasoline sold per day is reported in gallons and fractions of a gallon. But 100 gallons really means between 99.5 and 100.5 gallons while 100.5 gallons really means between 100.45 and 100.55 gallons.