Until recently, most larger-scale batteries were made using nickel and cadmium, but they were heavy, and lacked the long life needed to properly power cars.
直到最近，电池大多是用镍和镉制作的，但是他们太重，缺乏为汽车正确提供动力的长使用寿命。
2
Undertaking large scale vaccination campaigns places heavy financial and operational burdens on countries.
开展大规模预防接种运动使国家承受沉重的财政和实施负担。
3
Even so, on a scale where 10 was most truthful, native English speakers got a score of 7.5, people with mild accents a score of 6.95 and people with heavy accents a score of 6.84.