5.The doctor suggested that I should take a rest . 

-> advised sb to do sth : khuyên ai đó làm gì

-> suggest that + S + should + V-inf 

5a. Our teacher suggested that we should study harder .

->advised sb to do sth : khuyên ai đó làm gì

-> suggest that + S + should + V-inf  

6.It has been suggested that income tax should be abolished. 

-> It + be + suggested that + S  + (should) be +Vpp 

7.I suggest that you should replace this bulb with a saving - energy one 

 I suggest replacing this bulb with a saving - energy one .

-> S+ suggest that + S+ should + V-inf 

-> S + suggest + V-ing + ... 

8. I suggest that we should go for a walk in the park . 

I suggest going for a walk in the park . 

->S+ suggest that + S+ should + V-inf 

-> S + suggest + V-ing + ...