第一句：
systems 没问题,这里要加-s.
但,involve 不对,要变为：get/be involved in,即：...classes to get/be involved in ...
因为这个动词的用法是：involve sb.in (doing) sth.（使某人牵涉或卷入某事）
第二句：
doubtless改为undoubtedly,通常放在句首.且should be => is,才能表示语气肯定.
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...如楼下所说那个改为to be get involved in,,,应该也可以吧？另外那个毫无疑问的那句，还是把整句发上来 吧get involved in 表示动作，be involved in 表示状态，任选一个都行。如果要表达“应该是”，可以用 indisputably （毫无争议地），即：People's welfare should be indisputably the best indication of a nation's greatness.