Даны предложения, содержащие инфинитив. Необходимо найти функцию инфинитива. Сделайте, как

1) They were Norsemen of Scandinavia who in their ships braved Arctic seas to make their way to Greenland in 985 AD.

to make -- an adverbial modifier of purpose событие цели

2) Their method of reading was to read one line from left to right, then to come back and to read the next from right to left.

to read, to come back, to read part of a predicate (predicative) именная часть сказуемого

3) To preserve the traditions under these circumstances was very difficult and they were not preserved.

to preserve -- subject подлежащее

4) The right to organize a guild was granted to the first towns by the owner of the land who might be the king, abbot or some other powerful lord.

to organize -- attribute определение

be part of a compound verbal modal predicate часть составного глагольного модального сказуемого