26. ________ the help of their group， we would not have succeeded in the investigation.

A) Besides B) Regardless of C) But for D) Despite

27. ________ much is known about what occurs during sleep， the precise function of sleep and its different stages remains largely in the realm of assumption.

A) Because B) For C) Since D) While

28. John doesn‘t believe in ________ medicine; he has some remedies of his own.

A) standard B) regular C) routine D) conventional

29. Owing to __ competition among the airlines， travel expenses have been reduced considerably.

A) fierce B) strained C) eager D) critical

30. In Africa， educational costs are very low for those who are __ enough to get into universities.

A) ambitious B) fortunate C) aggressive D) substantial

26-30 CDDAB