The correct answer is A. Eleven high schools in the area have a chapter of SADD.
Step-by-step explanation:
In writing, small numbers are usually spelled while big numbers are written using figures or numerals. Also, the range of numbers varies according to each manual style as some state numbers from 1 to 10 should be spelled but others state numbers from 1 to 100 can be spelled. In all cases, if a sentence begins with a number this should be always spelled except in the case of years. This implies in the sentence presented the number should be "eleven" and not "11".
On the other hand, in terms of abbreviations manuals recommend to use capital letters and avoid the use of unnecessary periods between letters, also if the abbreviation is at the end of sentences and periods are used it is not necessary to add an extra period to end the sentence. According to this, the correct answer is "Eleven high schools in the area have a chapter of SADD."