I think expert is countable and it should be socks

Cotton: Could be both depending on the meaning: - As the cloth made of white fibres of a plant it is uncountable, while it is countable as a piece of clothing made of cotton. - Her shirt is made of cotton ( uncountable) - She bought a selection of pretty colourful cottons ( countable) Clothing : is uncountable. Labor: Is uncountable even in its plural form 'labors' it is still uncountable. Expert : is countable Sock: is countable and it is usually used in the form of '' pair of socks". Price: could be both depending on context. - House prices have fallen ( countable) - Large cars are dropping in price ( uncountable) Demand: Could be both as well depending on its meaning. It is countable when it refers to a statement of one's wants and needs and uncountable when it refers economically to the amount of a product or service that people want. - He was sympathetic to their demands ( countable) - Demand for new housing is increasing ( uncountable) Cost: can be both countable and uncountable. When it is the price paid to acquire, produce, accomplish, or maintain anything it is uncountable. In 'law' referring to money due to a court for services in a cause ,it is countable. - The low cost of a good meal ( uncountable) - You have a lot of costs to pay for that cause. ( countable) Clothes: uncountable Money: Money is uncountable ,although it has an archaic use , that might be still used in law 'moneys ' referring to a pecuniary sum or income. Holiday: Depends what you are talking about, if it is a vacation then it is uncountable , if it is talking about days you take off ,where work is suspened ,then it is countable. - No mail is delivered on federal holidays ( countable) - I think you should take a short holiday to Spain.(uncountable)