Criterion for a primary standard
A substance used as a primary standard in titrimetric analysis should be:

• very pure,
• stable in air,
• non-hygroscopic / non-efflorescent,
• of high molar mass,
• easily soluble (if needed),
• should not react with air such as absorbing $\mathrm{CO_2}$ or getting oxidized/reduced.

Examine each compound

A. $\mathrm{Na_2Cr_2O_7}$
Sodium dichromate is stable, fairly pure, and is commonly used as a primary standard oxidizing agent.
So, it can be used as a primary standard.

B. Oxalic acid
Oxalic acid (generally as hydrated oxalic acid) is stable and commonly used as a primary standard in redox titrations.
So, it can be used as a primary standard.

C. NaOH
Sodium hydroxide is not suitable as a primary standard because it is hygroscopic and absorbs $\mathrm{CO_2}$ from air, changing its composition.
So, it should not be used.

D. $\mathrm{FeSO_4\cdot 6H_2O}$
Ferrous sulfate is easily oxidized by air from $\mathrm{Fe^{2+}}$ to $\mathrm{Fe^{3+}}$, so it is not stable enough for use as a primary standard.
So, it should not be used.

E. Sodium tetraborate
Sodium tetraborate (borax) is actually a well-known primary standard for acid-base titrations because it is stable and can be obtained pure.
So, it can be used as a primary standard.

List of substances that should not be used as primary standards

The unsuitable ones are: $\boxed{\text{C and D}}$

Match with given options

Given options are:

• A: C, D and E Only
• B: B and D Only
• C: D and E Only
• D: A, C and D Only

Our derived set is $\{C, D\}$, which is not exactly present in the options.

Comparison with stored answer

Stored correct answer is D = A, C and D Only.
But $\mathrm{Na_2Cr_2O_7}$ is generally considered a valid primary standard, so including A is incorrect. Also E (borax) is a primary standard, so excluding it is correct.

Hence, the stored answer appears inconsistent with standard analytical chemistry facts.