2
no spaces
1
2 Spaces
In typing, proper style is 2 spaces after a period (.), as well as after a colon (:).
One space is sufficient.
2
no spaces
1
50 million gazillion
Unlike the period at the end of a sentence (which have one or two spaces), the period following an abbreviation only needs one space. This is the general rule for abbreviations such as Dr., Jr., or Sr.
One.
The number of spaces that follow an abbr. is one.
2 Spaces
In typing, proper style is 2 spaces after a period (.), as well as after a colon (:).
Mr. and Mrs. take a period, but Miss does not at it is not an abbreviation.
It used to be 2 spaces but nowadays it is only 1.
one