Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

Paper made out of limestone – Stone Paper – Production and properties of environmentally friendly paper substitutes.

Stone paper is made out of powdered limestone (calcium carbonate). This type of paper is more tear-resistant than conventional paper, even at low grammages. Moreover this material is extremely hard-wearing. Additionally, the flame retardant material is water-resistant, as well. Since neither wood fibres nor water are needed in the production process, stone paper is a sustainable and environment-friendly material. It also convinces with its noble and velvety feel. Due to its stability, it can also be described as rockboard.

Calcium carbonate (CaCo3) is a naturally occurring raw material which is available in almost inexhaustible quantities. The lime powder used for the production of stone paper is usually a waste product from quarries. This means that the quarry waste does not have to be mined separately, but can be processed immediately according to the cradle-to-cradle principle. The environmental friendly ecological binder, which is added to one fifth to the mineral powder, is also a waste product being used for the production of stone paper. The ecological binder gives strength to the paper alike material. This thermoplastic bio-plastic can e.g. be obtained from sugar cane waste.

The substitution product consists of 80% stone powder and 20% organic plastiC. The two materials are blended and pressed together under great pressure and processed into paper webs. During the patented manufacturing process neither bleaching agents nor acids, bases or fluorescent chemicals are used and not even a single tree is cut down. The energy requirement is only half as great as of the conventional cellulose paper. Compared to virgin fibre paper, there is also no residue or waste during processing. As a result,”paper” made of stone and being a sustainable alternative is now playing an increasingly important role in the manufacture of promotional items.

Stone Paper has been developed in the late 1990s in East Asia, where it is still produced today. In Asia and the USA, paper substitutes are already widely used. In Germany, the distribution and use of this miracle material is still very young, but above all, it is becoming more and more popular, especially in the field of ecological carrier bags.

What is " hard-wearing " in paragraph 1 closest in meaning to?