Harsh climates, such as extreme heat, cold, or aridity, can discourage settlement due to the challenges they pose for agriculture, water availability, and overall survival. Inaccessibility due to rugged terrain, such as mountains or dense forests, can also discourage settlement by limiting trade, communication, and resource access. Natural hazards like frequent earthquakes, volcanic eruptions, or hurricanes can make an area undesirable for settlement due to the risks they present to human life and infrastructure.

The environment in the past was likely less polluted and more pristine compared to the present. There were fewer human activities causing habitat destruction, species extinction, and climate change. Today, we face more environmental challenges due to increasing population, industrialization, and resource exploitation.

Cynthia digs her heels into the sand.

Present Simple: I should accept your challenge. Past Simple: I should have accepted your challenge.

The past tense of 'am' is 'was'.

The present progressive tense of the word "ask" is "asking."

Yes, an auxiliary verb of present tense helps to form different tenses or aspects of a verb in the present. Examples include "do," "does," "is," "are," "am," "have," and "has."

The present tense for "to be" is "am," "is," or "are," depending on the subject: I am, you are, he/she/it is, we are, they are.

"Estoy escribiendo en mi cuaderno" is in the present progressive tense. It combines the present tense conjugation of "estar" (estoy) with the gerund form of the verb "escribir" (escribiendo) to indicate an action that is currently in progress.

The present tense for "left" is "leave" or "leaves" depending on the subject.

The perfect tense of "ring" is "rung." For example, "I have rung the bell."

The present tense of the sentence "She turns the light on" is "She turns the light on."

The present perfect tense of "swell" is "has swelled" or "have swelled," depending on the subject of the sentence. For example, "The river has swelled after heavy rains."

The present form of "put" is "put."

The present form of "am" is "am". It is used in the first person singular present tense.

Fly -- I fly to work

Flies -- She flies to work

Flying -- We are flying to work

Coming IS the present participle of come. The present participle is always verb + ing.

The correct present tense for "ellos" in Spanish is "ellos hablan" which means "they speak".

The present simple passive form of "send" is "is/are sent".

The present tense of "conceal" is "conceals" for third person singular (he/she/it) and "conceal" for all other subjects.

hide itself

If the verb in the independent clause is in the present tense, the verb in the indirect quotation should also be in the present tense. This maintains consistency in the overall tense of the sentence.