Which of the following describes the electron sharing between hydrogen and fluorine a. hydrogen and fluorine share one electron with each other b.
hydrogen and fluorine share seven electrons with each other c. hydrogen shares seven electrons, while fluorine shares one electron. d. hydrogen shares one electron, while fluorine shares seven electrons

Hydrogen has one electron in its outermost shell, while fluorine has seven electron in its outermost shell, hence both hydrogen and fluorine needs a single electron to complete its outermost shell. 
That's why there is a single bond between hydrogen and fluorine.
Hence both hydrogen and fluorine share one electron with each other, so option "A" is correct.