正在/在（Adv.） "in process of" 
    
    正在，an adverb, is always in the preverbal position to indicate an action in process. Sometime, 正在 can be replaced by 在。
    呢，a final particle at the end of a sentence, can co-occur with 正在in a sentence to emphasize the continuation of an action.
                  
                Subj. +正在/在+VP+（呢）
Examples:
1. 他们正在开会呢。
They are having a meeting.
2. 我们正在讨论投资问题。
We are discussing the question on how to invest right now.

Substitutive drills: