To find the number of people who can speak only English, we need to subtract the number of people who speak multiple languages from the total number of people who can speak English.

From the given information, we know that 15 people speak English and French, 13 people speak English and German, and 5 people speak all three languages.

To find the number of people who speak English, we can add up the number of people who speak English and French (15), the number of people who speak English and German (13), and the number of people who speak all three languages (5). This gives us a total of 33 people.

However, since 30 people can speak German and 30 people can speak French, some of the people who speak both English and German, or both English and French, must also speak either German or French. We need to subtract the number of people who can speak both English and French from the total number of people who speak English.

Therefore, the number of people who can speak only English is 33 - 15 = 18.

The correct answer is not provided in the options.