1. A. happy
   (The others are nouns or verbs, while "happy" is an adjective.)

2. B. litter
   (Litter refers to small pieces of trash or waste, while rubbish refers to general waste material. The other options are not related.)

3. C. apply
   (The verb "apply" stands out because it refers to making a formal request or using something, while the others are related to decision-making or relaxation.)

4. A. mother
   (The word "mother" stands out because it refers to a person, while the others are abstract concepts or categories.)

EXERCISE 2:

1. D. hobby
   (All other words have the stress on the first syllable, but "hobby" has stress on the first syllable as well, but it's the only one with an "o" vowel.)

2. A. great
   (The stress pattern of "great" is different from the others, as it's a monosyllabic word.)

3. D. garbage
   ("Garbage" is stressed on the first syllable, while the others are stressed differently.)

4. C. happen
   ("Happen" has stress on the first syllable, unlike the others.)

5. C. popular
   ("Popular" is stressed on the first syllable, while the others are stressed on the second syllable.)