【简答题】推理证明下列各题的有效结论 (1) p → ( q ∨ r ), ( t ∨ s ) → p, ( t ∨ s ) Þ q ∨ r (2) p ∧ q ,( p ↔ q )→ ( t ∨ s ) Þ ( t ∨ s ) (3) Ø ( p → q )→ Ø ( r ∨ s ), ( q → p )∨ Ø r , r Þ p ↔ q (4) p ∧ q → r, Ø r ∨ s, Ø s Þ Ø p...
【简答题】We are still students now. We have to ____ our parents to live and to study. (依靠)
【简答题】We are still students now. We have to ______________ (依靠)our parents to live and to study.
【简答题】For our homework tonight, we have to write a______(describe) of the street where we live.
【判断题】切削铸铁等脆性材料,宜选用YT类硬质合金。
【单选题】We have to live our income.