Agriculture is undoubtedly the most important sector in the economies of most non-oil expo

rting African countries. It【C1】______ about 30% of Africa's GDP and contributes【C2】______ 50% of the total export value,【C3】______ 70% of the continent's population depending on the sector for their【C4】______ . Production is subsistence in nature with a high【C5】______ on the rain. The debate on climate change and its impacts on agriculture is【C6】______ very crucial to the very survival of the continent and its people. The continent is particularly【C7】______ to climate change because it includes some of the world's poorest nations.

The climate in Africa is【C8】______ tropical in nature, which is broadly【C9】______ into three main climatic zones:【C10】______ equatorial, dry, and temperate(温带). Within these zones, altitude and other localized【C11】______ also produce distinctive regional climates.

Climate change,【C12】______ indicated by prolonged drought is one of the most serious climatic【C13】______ affecting the agricultural sector of the continent. As most of the agriculture activities in African countries hinges on rain fed, any adverse changes in the climate would likely have a【C14】______ effect on the sector in the region.

【C15】______ changes in the climate may affect the whole continent, its【C16】______ may vary across the continent. In northeast Africa, more intense dry periods and shorter wet seasons are expected to affect even huge river systems such as the Blue Nile, leading to serious water shortages and【C17】______ consequences to the agriculture and forestry sectors throughout the region. East and Central Africa will also see its agricultural【C18】______ decline. Coastal areas may also be affected by rising sea levels and intrusion of salt water into inland freshwater resources. The staple food for the region, maize, is particularly susceptible to drought. Wetlands of international importance and wildlife are also under threat from【C19】______ in Southern Africa. Climate change, therefore, is expected to worsen the food supply,【C20】______ , exacerbate the widespread poverty in the region.

【C1】

A．constitutes

B．institutes

C．command

D．compose