  We discuss the properties of the progenitors of core collapse SNe, as they
can be deduced from rotating stellar models of single stars. The type of the SN
progenitor was determined from the surface abundances at the pre-SN stage. The
type of the SN event was obtained from the masses of hydrogen and helium
ejected at the time of the core-collapse SN event. We find that the minimum
amount of helium ejected by a core-collapse SN (of whatever type) is around 0.3
MSun. There is no difference between the WC and WO stars in the ejected masses
of helium, CNO elements, and heavy elements. Also no difference is expected
between the chemical composition of a WC star resulting from a normal or a
homogeneous evolution. The progenitors of type Ib SNe are WNL, WNE, or less
massive WC stars. Those of type Ic are WC and WO stars. WO stars are produced
in a limited mass range (around 60 MSun) and only at low metallicity (for <=
0.010) as already found. The WO stars are the progenitors of only a small
fraction of type Ic. Present stellar models indicate that, at solar
metallicity, there is about 1 type Ib SN for 1 type Ic, and this ratio rises to
3 type Ic for 1 type Ib SN at twice solar metallicity. At this metallicity,
type Ic's are more frequent than type Ib's because most massive stars that go
through a WNE stage evolve further into a WC/WO phase. Current models can
account for the observed number ratios SN Ib/SN II and SN Ic/SN II and for
their observed variation with the metallicity. In case no supernova occurs when
a black hole is formed, single-star models can still account for more than half
of the observed (SN Ib+SN Ic)/SN II ratio for Z >= ZSun. For the GRB rate, our
models produce too large a number for such an event, even if we restrict the
progenitor to the WO stars.
