Fill in the Blanks

 'Now I go twice a month' indicates that the preceding part is about what I did in the past. So, the appropriate use is 'used to'.

 This is an imperative sentence (instructiuon). But here the candidates are being told not to write. So the modal used has to be 'must not'. 'Need not' would mean as if they could write if they wanted. 

 Some completion is expected in future. So' 'will have'

 The fever must have happened before 'he said'. 'For three days' indicates completion as well as continuation. So, 'had been suffering'

 The obligation is moral or social. There is no advisory or compulsion. In such cases the appropriate modal use is 'ought to'.

 'Call me a liar' with a question mark means that the person is protesting. The only verb that indicates challenge is 'dare'. How dare you...? 

 'As the ship sank' is in the simple past tense. At that time whatever the sailors did also has to be in the simple past tense. 

 Lest is followed by the usage of 'should'.

 This means that he does not have the courage. Hence, 'dare'

 The snake's action and the man's action are concurrent. Hence, the same simple past tense (wound), Hence, 'wound' is correct.

 'In my youth' is a reference to the past. The correct filler will be simple past 'took' or 'used to take'. 

 'Had' is antecedent in time to 'would have'. 

 'If' or 'should' you, convey the same sense.

 Sported in some means to wear something (i.e. he sported a brand new, gold watch).

The correct spelling is 'addressed', which contains a double 'd' and a double 's'.