第一句：
systems 沒問題,這里要加-s.
但,involve 不對,要變?yōu)椋篻et/be involved in,即：...classes to get/be involved in ...
因為這個動詞的用法是：involve sb.in (doing) sth.（使某人牽涉或卷入某事）
第二句：
doubtless改為undoubtedly,通常放在句首.且should be => is,才能表示語氣肯定.
整句：Undoubtedly,people's welfare is the best indication of a nation's greatness.
或者：People's welfare is undoubtedly the best indication of...如樓下所說那個改為to be get involved in,,,應(yīng)該也可以吧？另外那個毫無疑問的那句，還是把整句發(fā)上來 吧get involved in 表示動作，be involved in 表示狀態(tài)，任選一個都行。如果要表達“應(yīng)該是”，可以用 indisputably （毫無爭議地），即：People's welfare should be indisputably the best indication of a nation's greatness.