关于else　[金字塔]

请问，多个条件选择时，是否需要加else，即

if.............then begin.....................end

if.............then begin.....................end

if.............then begin.....................end

还是要

if.............then begin.....................end

else if.............then begin.....................end

else if.............then begin.....................end

??

加与不加有什么区别吗