Department of the Army TRADOC Reg 350-XX

(d) The probability of guessing a four-choice item is 25 percent. As implausible distracters, or poorly designed alternatives, are eliminated, the probability is quickly increased to 50 percent, which is no better than a true-false item. A lengthy list of “Dos and Don’ts” for multiple-choice test item construction is found in JA 350-70-5.7b. ................
................