Passage 4: Questions 33-37        Disposing of waste has huge environmental impacts and can cause serious problems. In manycountries around the world, much is buried in landfill sites. Some waste will eventually rot, but not all, andin the process it may smell, or generate methane gas, which is explosive and __(33)__ the greenhouseeffect. Leachate__ (34)__ as waste decomposes may cause pollution. Badly-managed landfill sitesmay attract vermin or cause litter.       A priority is to move from reliance on waste dumps that offer no environmental protection, to wastemanagement systems that__ (35)__ useful resources within the economy. Waste __(36)__ at sourceand use of specialized waste processing facilities to separate recyclable materials has a key role. Disposalof residual waste after extraction of material resources __(37)__ engineered landfill sites and/orinvestment in waste-to-energy facilities.
【題組】33.
(A) hinges on 
(B) wears out
(C) looks into
(D) contributes to