A problem about pkg_deinstall

[lacalling]

I have some problems about pkg_deinstall.

pkg_deinstall -R deletes packages depended recursively.

but it seems to crashes some other packages.

for example,i installed pkg A,it depends on pkg b,c,d.

pkg_deinstall -R will deletes A,b,c,d.

but if b is depended by some other pkg X which i use,X probably will crash.

i read man pkg_deinstall,but got no further info.

could anyone kindly help me to find out how to delete pkgs only depended by
A?