有if的句子怎么读,急!在线等,像If I have no food,I will die.升降音怎

有if的句子怎么读,急!在线等,像If I have no food,I will die.升降音怎么读句子的升和降音一直没搞懂,那位大仙帮忙告诉我,急!在线等待!从句在后怎么读？像what will tigers do if they have babies？if前的是升是降？if后的呢？帮忙说清楚点，追分追分！！！！！！急！！！！！！