The grammatical category of tense

 
The grammatical category of tense is defined as a category which expresses the relations between the time of the 
action and the moment of speech. 
English, like the other Germanic languages, Japanese, Persian, and so on, has only two morphological tenses, past and non-past (alt. present–future). These are distinguished by verb form, by either ablaut or suffix (sings ~ sang, 
walks ~ walked). The non-past may be used to reference the future ("The bus leaves tomorrow"). 
Tense and aspect in English 
Tense Simple Perfect Continuous/Progressiv
e 
nonpa
st 
past 
-Ø/-s 
-ed, -t, ablaut, etc. 
has/have -en, -ed, ablaut, 
etc. 
had -en, -ed, ablaut, etc. 
am/is/are -ing 
was/were -ing 
nonpa
st 
past 
go, goes 
went 
have/has gone 
had gone 
am/is/are going 
was/were going 
The future can also be referenced using forms with an auxiliary verb, particularly shall or will, and these are often 
called the "future tense". 
2. Constituent Structure of the Sentence. 
In grammar, the relation between a linguistic unit (i.e., a constituent) and the larger unit that it is a part of. 
Constituency is traditionally represented by bracketing or tree structures. 
A constituent can be a morpheme, word, phrase, or clause. For instance, all the words and phrases that make up a 
clause are said to be constituents of that clause. 
Еще нужно искать; инфы в Инете мало. 
3. Analyze the sentences.