下列各式中,计算正确的是( )
A:2x+x=2x2
B:153.5°+20°3′=173°33′
C:5a2-3a2=2
D:2x+3y=5xy
从125m高的桥面上每隔一定时间从同一点静止释放完全相同的小钢球.当第11个小钢球刚要下落时,第1个小钢球刚好落地.不计一切阻力,求:
—Could you tell me the________ of making such tasty cakes?
—Well, I just follow the directions in the cookbook.