In this task, you will be given a set of steps that are required to answer a specific question. Your job is to generate that question. Each given step refers to either an entity (known or unknown), a propery of an entity or a query operation (count, group, union, etc.) Knowing those operations and how they appear in the input may help you generate more accurate questions.
 Select: A select step is used to return a set of objects. There are no references to previous steps in a select step. template: Return [attributes]
 Filter: A filter step is used to return results from a previous step to which a certain condition applies. template: Return [#step] [condition]
 Project: A project step should return certain attributes of the results of a previous step. template: Return [attributes] of [#step]
 Aggregate: An aggregate step returns an aggregator function applied on a step's result. template: Return the [aggregator] of [#step].
 Group: A group step is an aggregator applied on attributes. template: Return the [aggregator] of [#step] for each [attribute]
 Superlative: A superlative step is used to return the result with a highest/lowest attribute among other results. template: Return [#step1] [where] [#step2] [is] [highest / lowest]
 Comparative: A comparative step is used when we need to compare an attribute with a number to filter results. template: Return [#step1] [where] [#step2] [comparator] [number] 
 Union: A union step is used to return results of two steps together. template: Return [#step1] [or / ,] [#step2]
 Intersection: An intersection step returns the result that two steps have in common. template: Return [attribute] of both [#step1] and [#step2]
 Discard: A discard step returns result of a step and excludes result of another step from it. template: Return [#step1] besides [#step2]
 Sort: A sort returns result of another step in a specific order. template: Return [#step1] [ordered / sorted by] [#step2]
 Is true: An is true step checks a condition on another result and returns a true or false. template: Return [is / if] [condition]
 Arithmetic: An arithmatic step operates an arithmatic operation on one or more steps. template: Return the [arithmetic op.] of [#step1] [and] [#step2].

#1 return troops 
#2 return #1 that was  lost on 29 April 1918 
#3 return #2 that was  the  Whites 
#4 return #2 that was  the  Reds 
#5 return number of  #3 
#6 return number of  #4 
#7 return which is highest of #5 ,  #6
Who lost more troops on 29 April 1918 - the Whites or the Reds?

#1 return objects 
#2 return #1 that are green 
#3 return #1 that are yellow 
#4 return number of  #2 
#5 return number of  #3 
#6 return sum of #4 and  #5
how many objects are green or yellow?

#1 return trains 
#2 return stations #1 pass 
#3 return #1 where #2 is  not London 
#4 return names of #3

Find the names of the trains that do not pass any station located in London.