Read the following passage and mark the letter A, B, C or D to indicate the correct word or phrase that best fits each of the numbered blanks.

Today, English is ___(1)___ second of three most popular mother tongue in the world, with an estimated 430-400 million ___(2)___. But, crucially, it is also the common tongue for many non-English speakers the world over, and almost a quarter of the globe’s population - maybe one and a half or two billion people - can ___(3)___ it and have at least some basic competence in its use, whether written or spoken.
It should be noted here that statistics on the numbers around the world who speak English are unreliable at best. It is notoriously difficult ___(4)___ quite what is meant by “English speaker”, let alone the definitions of first language, second language, mother tongue, native speaker, etC. What level of competency counts? Does a thick creole (English based, but completely incomprehensible to a native speaker) count? Just to add to the confusion, there are a least 40 million people in the nominally English-speaking United States ___(5)___ do NOT speak English. In addition, the figures, of necessity, combine statistics from different sources, different dates, etc. You may well see large variations on any statistics quoted.