... reaches Level < /b> B lesson 31 1. …………. business, a merger is a combination of two or more corporations under one management. DA. The B. At C. On D. In 2. …………. of commodities by air began in ... becomes easier. B A. The B. Once B. the desire to sleep C. to desire sleep is D. the desire to sleep who 13. Although dissimilar in almost every other respect, birds and insects have both ... D. Even 14. The wheel, …………. has remained important for 4, 000 years, is one of mankind’s first inventions. CA. how B. when C. which D. about 15. …………. children master the basics, advanced...