think 究竟加 to do sth 还是 doing sth.不是think of

think to do sth.想要,打算[+to-v][+(that)]
At first he thought to tell her,then he changed his mind.
他原来打算告诉她的,后来改变主意了.
think 后面经常跟从句.
think 后面要是加doing sth.时,总是先加介词,再加doing sth.