English tense explanations

I want to try and carry out an ..........
experience
endeavour
endurance
experiment

My ......... is to explain the different uses of the tenses.
problem
plan
situation
thought

The main question is knowing where you .........?
commence
initiate
start
activate

As you ......... know there are many tenses in English.
probably
certainly
sometimes
doubtfully

The problem is ......... you can tell the difference
what
how
which
where

between, for ........., the Present and Present Perfect.
case
sample
instant
example

But I should ......... myself from talking about
control
halt
stop
exact

particular tenses ......... I've talked about tenses in general.
since
before
although
if

Please ......... me for going on to the middle of my story
forgive
forget
forbid
forefend

when I should be thinking about the ..........
initial
genesis
first
beginning