Which of these is opposite to 'invalid' as used in paragraph 5?

What is validity and the different types?

Which of the following is the opposite of the word "legitimate"?falseinvalidsubjectivesimilar

Identify the part of the sentence that contains an error.Pollution taxes are widely accepted (A)/ as often more preferable than (B)/ rigid regulations on pollutants. (C)/ No error (D)A (D)

69. Given C: Proposition No cheater is honest is true. Therefore, some cheaters are honest is false. With reference to the Given C proposition, which of the following rules is applicable? a. Contradictories cannot be both false, if one is true, the other is false. b. Contradictories cannot be both false, if one is false, the other is true. c. If the particular statement is true, the subaltern is doubtful. d. Contraries can be false at the same time. 70. With reference to the Given C proposition, which following rule is applicable? a. Sub- contratries can be true at the same time. b. Contraries can be false at the same time. c. Contradictories cannot be both false; if one is false, the other is true. d. If the universal is false, the subaltern is doubtful. 71. Which logical opposition applies this rule; 1. If one proposition is true, the other is false. 2. If one proposition is false, the other is doubtful a. Contradictory b. Subcontrary c. Contrary d. Subaltern

1. Which decision error is the most problematic?