Part of Determining the Drake Factor R* Is Determining What

Part of determining the Drake factor R* is determining what is a "Sun star," a star around which a habitable planet could orbit.What is the thinking concerning low-mass stars,that is,stars with masses less than about half a solar mass? (These are stars cooler than M0 type main-sequence stars.)

A) Low-mass stars are highly desirable here because they tend to live longer and allow more time for life to develop and form a civilization.
B) Planets would have to orbit relatively close to low-mass stars in order to be warm enough to be in the habitable zone. But they are still acceptable as Sunlike stars.
C) Planets would have to orbit relatively close to low-mass stars in order to be warm enough to be in the habitable zone. But this means they will be tidally locked into synchronous rotation, with one very hot side and one very cold side-not an acceptable situation.
D) Photosynthesis, the main energy-production mechanism in green plants on Earth, works best with shorter wavelengths of light. These low-mass red stars tend to produce fewer of these shorter wavelengths and thus could not support efficient photosynthesis.