Some Prepositions

A, an, for, in
.
I’m a financial controller. (a/an + job)
.......an engineer.
.
I work for ATT. (for + employer)
.
I’m in marketing. (in + type of work)
............the Hospitality Industry
............chemicals.
.
In, on, at
.
In
1999 (years)
August (months)
the winter (seasons)
the afternoon (parts of the day)
.
On
Saturday (days of the week)
May 2nd (dates)
.
At
05:30 A.M. (hours of the clock)
the end of the war (points in time)