Have To/ Must/ Should/ Shouldn't/ Don't Have To/ Had To/ Didn't Have To

Explanation
The correct answer is "has to" because the sentence is in the present tense and the word "has" is used to indicate possession or obligation. In this case, the person is experiencing unbearable pain in her back, which creates an obligation or necessity for her to see a doctor.

Explanation
The word "must" is the correct answer because it indicates a strong obligation or necessity. In this sentence, it implies that there is a requirement to come to work on time, and failure to do so will result in the boss being furious.

Explanation
The correct answer is "don't have to." This is because the phrase "don't have to" indicates that there is no obligation or requirement to study now that the exams are over. It implies that studying is optional and not necessary.

Explanation
The correct answer is "had to". This is because the sentence is in past tense and the phrase "last week" indicates that the action already happened. "Had to" is the past tense form of "have to", which expresses an obligation or necessity to do something. In this case, the speaker had an obligation to visit their sick friend.

Explanation
The correct answer is "should." This is because the sentence is talking about losing weight, which implies that it is a recommendation or suggestion. "Should" is commonly used to give advice or express what is considered the best course of action.

Explanation
The sentence states that throwing garbage in the street is not allowed. The word "mustn't" is used to express prohibition or a strong obligation not to do something. Therefore, the correct answer is "mustn't" because it aligns with the prohibition mentioned in the sentence.

Explanation
The correct answer is "had to" because it indicates a past obligation or necessity to sleep early in order to wake up early. This implies that there was a requirement or expectation to go to bed early on the previous night.

Explanation
The correct answer is "should" because it implies that it is not appropriate or advisable to argue with teachers or parents. The word "should" suggests a moral obligation or a recommended course of action.

Explanation
The correct answer is "don't have to." This is because the sentence states that the speaker has a housemaid, which implies that they do not need to do the washing up themselves. "Don't have to" indicates the absence of obligation or necessity to perform the action.

Explanation
The word "must" is used to express a strong obligation or necessity. In this context, it implies that it is necessary or mandatory to respect the traffic rules. The other options do not convey the same level of obligation or necessity. "Should" suggests a recommendation rather than a requirement. "Have to" and "had to" indicate a lesser degree of obligation, implying that it is a personal choice or a past requirement rather than an ongoing necessity.