Identify the correct statement(s) among the following:

(A) If three electrical cells each of emf, E and internal resistance r are connected in series to a resistance R, the current drawn from them is $3E/(R+3r)$.
(B) If these three cells are connected in parallel combination, across resistance R then the current drawn will be $E/(3R+r)$.
(C) If the two cells are connected in series and then one in parallel which are then connected across resistance R, then the current drawn will be $2E/(2R+2r)$.
(D) In a mixed grouping of cells, current will be maximum when total external resistance is equal to total equivalent internal resistance.

Choose the correct answer from the options given below.

(A) and (D) only

The correct answer is Option (2) → (A) and (D) only

(A) Three cells in series: total emf = $3E$, total internal resistance = $3r$.

Current $I = \frac{3E}{R+3r}$ ✅ Correct.

(B) Three cells in parallel: equivalent emf = $E$, equivalent internal resistance = $\frac{r}{3}$.

Current $I = \frac{E}{R+\frac{r}{3}} = \frac{3E}{3R+r}$, not $\frac{E}{3R+r}$. ❌ Incorrect.

(C) Two in series (emf $=2E$, resistance $=2r$) in parallel with one cell (emf $=E$, resistance $=r$). Equivalent emf is not $2E$ and denominator not $2R+2r$. ❌ Incorrect.

(D) For maximum power transfer, external resistance $R =$ equivalent internal resistance $r_{eq}$. ✅ Correct.

Correct statements: (A) and (D)