The correct statement(s) regarding sugars is(are)
Given: Specific rotations of L-(−)-glucose and L-(+)-fructose are −52.5° and +92.5°, respectively.

The correct statements regarding sugars are:

1. Fructose gives a positive Fehling’s test because it isomerises to glucose and another aldohexose in the presence of Fehling’s reagent.
2. Invert sugar is an equimolar mixture of D-glucose and D-fructose formed after hydrolysis of the corresponding disaccharide.

Detailed Explanation of Each Statement:

Statement 1: Oxidation with HNO₃
Nitric acid (HNO₃) is a strong oxidizing agent. It oxidizes both glucose and gluconic acid to saccharic acid (dicarboxylic acid). Therefore, the claim that glucose is not oxidized to saccharic acid by HNO₃ is incorrect.

Statement 2: Fehling's test for Fructose
Although fructose contains a keto group (ketose), it reduces Fehling's solution (gives a positive test). In the presence of the basic Fehling's reagent, fructose undergoes keto-enol tautomerism (Lobry de Bruyn-Alberda van Ekenstein transformation) to isomerize into glucose and mannose (another aldohexose), both of which are reducing aldohexoses that react with Fehling's reagent.

Statement 3: Definition of Invert Sugar
Invert sugar is defined as an equimolar mixture of D-(+)-glucose and D-(-)-fructose produced by the hydrolysis of sucrose (a disaccharide).

Statement 4: Specific Rotation of Invert Sugar
Let us calculate the specific rotation of invert sugar formed by hydrolysis of sucrose:
The specific rotation of D-(+)-glucose is +52.5° and that of D-(-)-fructose is -92.4° (or -92.5° as given in terms of L-enantiomer magnitude).
For an equimolar mixture of D-glucose and D-fructose:

${\left[\alpha \right]}_{\text{mix}}=\frac{+52.5°-92.5°}{2}=\frac{-40°}{2}=-20°$

Hence, the specific rotation of invert sugar is -20° (or -19.97°), not -40°. Therefore, Statement 4 is incorrect.