A carbohydrate which cannot be hydrolysed to simpler compounds is called:
A) monosaccharide
B) disaccharide
C) polysaccharide
D) oligosaccharide

Hint: A carbohydrate is a biomolecule made up of carbon (C), hydrogen (H), and oxygen (O) atoms, generally in a 2:1 hydrogen–oxygen atom ratio (as in water), and therefore having the empirical formula $ {{\text{C}}_{\text{m}}}{{\left( {{\text{H}}_{\text{2}}}\text{O} \right)}_{\text{n}}} $ (where m may or may not be different from n). However, not all carbohydrates (e.g., uronic acids, deoxy-sugars like fucose) meet this exact stoichiometric criteria, and not all compounds that do meet this description are automatically classed as carbs (e.g. formaldehyde and acetic acid).

Complete Step By Step Answer:
The term is most commonly used in biochemistry as a synonym for saccharide, which refers to sugars, starch, and cellulose. Monosaccharides, disaccharides, oligosaccharides, and polysaccharides are the four chemical groups of saccharides. Sugars are the smallest (lowest molecular weight) carbohydrates, which are monosaccharides and disaccharides.
Monosaccharides, often known as simple sugars, are the most fundamental units of carbohydrates and the most basic type of sugar. Although not all molecules with this formula (e.g. acetic acid) are carbohydrates, the general formula is $ {{C}_{n}}{{H}_{2n}}{{O}_{n}} $ . They are generally white, crystalline solids that are water soluble. Only a few monosaccharides have a sweet taste, despite their name (sugars). Glucose (dextrose), fructose (levulose), and galactose are examples of monosaccharides. Disaccharides (such as sucrose and lactose) and polysaccharides are made up of monosaccharides (such as cellulose and starch).
Monosaccharides are polyhydroxy-carbonyls, which are the most basic carbohydrates. The carbonyl group can be either an aldehyde (aldoses including glucose, galactose, and ribose) or a ketone (these are ketoses, like fructose, ribulose). Monosaccharides have three to nine carbon atoms, however those with five carbon atoms, known as pentoses (D-ribose; D-2-deoxyribose; L-arabinose; D-xylose), and six carbon atoms, known as hexoses, are the most common (glucose, fructose, galactose and mannose).
Because monosaccharide is the simplest unit, it cannot be hydrolyzed into simpler molecules.
Hydrolysis of disaccharides, polysaccharides, and oligosaccharides to monosaccharides is possible.
Hence option A is correct.

Note:
Carbohydrates are essential for good nutrition and may be found in both natural and processed meals. A polysaccharide is starch. Cereals (wheat, maize, rice), potatoes, and processed foods made with cereal flour, such as bread, pizza, and pasta, are high in it. Table sugar (sucrose, derived from sugarcane or sugar beets), lactose (rich in milk), glucose, and fructose, each of which exist naturally in honey, many fruits, and certain vegetables, are the most common sugars in the human diet. Drinks, as well as numerous prepared meals like jam, biscuits, and cakes, are frequently sweetened with table sugar, milk, or honey.