Which word fits these sentences?
A Persian rug with beautiful patterns lay/laid on the floor.
I think lay for present tense?
The temperature has raised/risen four degrees in the past hour.
I think risen because there is no object?
Great job with your analysis! You're correct in both cases.
In the first sentence, "A Persian rug with beautiful patterns [lay/laid] on the floor," the correct word is "lay." The present tense of the verb "to lay" is "lay." Since the subject of the sentence is a Persian rug, which is the one laying (placing itself) on the floor, we use the present tense verb "lay."
To further clarify, if the sentence were in the past tense, it would be "A Persian rug with beautiful patterns [laid] on the floor," because "laid" is the past tense version of "lay."
In the second sentence, "The temperature has [raised/risen] four degrees in the past hour," the correct word is "risen." This is because the verb "to rise" does not require an object; it denotes self-motion. The temperature itself is increasing, so we use the past participle form "risen" after the helping verb "has."
On the other hand, "to raise" is a transitive verb that requires an object. For example, you could say, "I raised the temperature four degrees by turning up the thermostat." In this case, "raised" is the correct past tense form to match with the object, "the temperature."
Remember, analyzing the subject, the tense, and the verb's transitivity can help you determine the correct word to use in a sentence. Keep up the great work!