1. Electronic configurations of copper ions

Copper has atomic number $29$.

Its ground-state electronic configuration is:

So,

• $\mathrm{Cu}^+$ : $[Ar] \, 3d^{10}$
• $\mathrm{Cu}^{2+}$ : $[Ar] \, 3d^9$

2. Check statement (A): Cu(II) complexes are always paramagnetic

$\mathrm{Cu}^{2+}$ has configuration $3d^9$. A $d^9$ system has one unpaired electron, so Cu(II) complexes are paramagnetic.

Thus, statement (A) is correct.

3. Check statement (B): Cu(I) complexes are generally colourless

$\mathrm{Cu}^+$ has configuration $3d^{10}$. Since the $d$-subshell is completely filled, $d$-$d$ transitions are not possible. Therefore, Cu(I) compounds/complexes are generally colourless.

Thus, statement (B) is correct.

4. Check statement (C): Cu(I) is easily oxidized

$\mathrm{Cu}^+$ can be oxidized to $\mathrm{Cu}^{2+}$, but in aqueous chemistry it is more known to be unstable and undergo disproportionation:

However, compared with Cu(II), Cu(I) is indeed readily converted to Cu(II) because $\mathrm{Cu}^{2+}$ is more stable in aqueous medium. So the statement that Cu(I) is easily oxidized is taken as correct in standard inorganic chemistry context.

Thus, statement (C) is correct.

5. Check statement (D): In Fehling solution, the active reagent has Cu(I)

Fehling solution contains a Cu(II)-tartrate complex in alkaline medium. During reaction with aldehydes/reducing sugars, Cu(II) is reduced to Cu(I) oxide ($\mathrm{Cu_2O}$), the red precipitate.

So the active reagent initially contains Cu(II), not Cu(I).

Thus, statement (D) is incorrect.

6. Count correct statements

Correct statements are:

• (A) Correct
• (B) Correct
• (C) Correct
• (D) Incorrect

Hence, the number of correct statements is: