下列有关物质性质的比较中,正确的是( )①沸点:H2O>HCl>HF ②密度:四氯化碳>水>汽油 ③酸性:H3PO4>H2SO4>HClO4 ④离子半径:O2->F->Na+
They use computers to keep the traffic _______ smoothly.
If you leave the club, you will not be_____back in .
What I need is_____ book that contains ______ABC of oil painting.
Jenny nearly missed the flight______ doing too much shopping.
The CDs are on sale! Buy one and you get ______ completely free.