Determine the types of interactions and whether Cabibbo...?

[Poirot]

Homework Statement

By considering the type of particles involved and which quantum numbers are conserved, classify each of the following processes into weak, strong, EM and forbidden interactions. (“Forbidden” means that it can’t be weak, strong nor EM.) For processes which are weak, state which are Cabibbo allowed or suppressed.
(a) p + p → p + n + π⁺(π is a meson containing only u and d quarks/antiquarks.)
(b) π^- + p → p + p +π⁰
(c) K⁺ → π⁰ +e⁺ + ν_e (K is a meson containing an s quark/antiquark plus a u or d quark/antiquark.)
(d) K^- → π⁺ + π^- + e^- +ν_e(anti)

Homework Equations

Quantum numbers:
Charge, Q ≡ 2/3(N_u+N_c+N_t) - 1/3(N_d+N_s+N_b)
Baryon number, B ≡1/3(N_u+N_c+N_t + N_d+N_s+N_b)
Quark Number: N_q = N(q) - N(q(anti))
Lepton Number: L_e = N(e^-) -N(e⁺) + N(ν_e) - N(ν_e(anti)) (and similar for muon and taon)

The Attempt at a Solution

(a) I think this is weak and Cabibbo allowed. I think weak because there is a change in quark species and hence a change in charge so weak must be involved? and Cabibbo allowed as u→d.
(b) I think this is forbidden as Q is not conserved.
(c) I think this is weak and Cabibbo suppressed. Weak because change in species and suppressed as s-bar→u-bar.
(d) I think this is weak and Cabibbo suppressed. I think s→u but I'm really not sure what's actually going on here?

If someone could possibly explain a checklist/guide for determining the types of interactions that would be great. And also any explanation of what's happening in the interactions, for example (a) is there a W- boson coming off one of the quarks (Feynman) to transfer the charge?

Thanks for any help, it would be greatly, greatly appreciated.