To determine which of the given quantities are state functions, we need to understand the definitions of state functions and path functions in thermodynamics.

State Function: A property of a system that depends only on its current state, specified by variables like temperature (T), pressure (P), volume (V), and number of moles (n). The change in a state function depends only on the initial and final states of the system, not on the path taken to get from one state to the other. Examples include Internal Energy (U), Enthalpy (H), Entropy (S), and Gibbs Free Energy (G).

Path Function: A quantity whose value depends on the path followed during a process. Work (w) and heat (q) are the most common examples of path functions.

Now let's evaluate each option:

A: Internal energy (U)

1. Internal energy is the sum of all kinetic and potential energies of the particles within a system.
2. It is a fundamental property that defines the state of a system.
3. The change in internal energy, $ΔU = U_{final} - U_{initial}$, depends only on the initial and final states, regardless of the process (path) connecting them. For a cyclic process where the initial and final states are the same, $ΔU_{cyclic} = 0$.
4. Therefore, internal energy is a state function.

B: Irreversible expansion work (w_irr)

1. Work is defined as energy transferred due to a force acting over a distance. In thermodynamics, expansion work is done when a system's volume changes against an external pressure.
2. For an irreversible expansion against a constant external pressure $P_{ext}$, the work done by the system is given by $w_{irr} = -P_{ext}ΔV = -P_{ext}(V_{final} - V_{initial})$.
3. The value of $w_{irr}$ depends on the external pressure $P_{ext}$, which is a condition of the path, not just a property of the initial and final states of the system. For the same initial and final volumes, different values of $P_{ext}$ will result in different amounts of work.
4. Therefore, irreversible expansion work is a path function.

C: Reversible expansion work (w_rev)

1. For a reversible process, the work done is calculated by integrating the pressure over the change in volume: $w_{rev} = -∫_{V_i}^{V_f} P_{ext} dV$. In a reversible process, $P_{ext} = P_{int} = P$.
2. The value of this integral, $w_{rev} = -∫_{V_i}^{V_f} P dV$, depends on how the pressure $P$ changes with volume $V$ during the expansion. This P-V relationship defines the path.
3. For example, for an isothermal reversible expansion of an ideal gas, $P = nRT/V$, so $w_{rev} = -nRT \ln(V_f/V_i)$. For an adiabatic reversible expansion, $PV^γ = \text{constant}$, which leads to a different expression for work: $w_{rev} = (P_fV_f - P_iV_i)/(γ-1)$.
4. Since the work done depends on the specific path (isothermal, adiabatic, etc.) between the initial and final states, reversible expansion work is a path function.

D: Molar enthalpy (H_m)

1. Enthalpy (H) is a thermodynamic potential defined as $H = U + PV$.
2. Since Internal Energy (U), Pressure (P), and Volume (V) are all state functions, their combination, Enthalpy (H), must also be a state function.
3. Molar enthalpy ($H_m$) is an intensive property defined as enthalpy per mole, $H_m = H/n$. Since H is a state function, molar enthalpy is also a state function. It depends only on the state of the substance (typically defined by its temperature and pressure).

Conclusion: Based on the analysis, Internal energy (A) and Molar enthalpy (D) are state functions, while irreversible and reversible expansion work (B and C) are path functions. Therefore, the correct options are A and D.