For his science project, Austin wants to determine if the pH of standing rainwater changes over time. He collects rainwater and distributes it evenly in 5 jars and places them all indoors in a spot that does not receive a lot of sunlight to limit evaporation. Using a pH testing kit, he measures the pH of the water in the first jar on the 4th day, second jar on the 8th day, third jar on the 12th day, fourth jar on the 16th day and fifth jar on the 20th day. What is the independent, or manipulated, variable in Austin's experiment?

This question lacks options, the options are:

A. the number of days the rainwater was allowed to sit

B. the number of times the rainwater was observed

C. the change in the amount of rainwater due to evaporation

D. the change in pH of the rainwater over time

The answer is A

Explanation:

In an experiment, the independent variable is the variable that is changed or manipulated by the experimenter in order to effect a measurable response.

In this experiment, Austin is trying to determine how time changes the pH of standing rainwater. He collects rainwater and distributes it evenly in 5 jars, which he measured the pH at different days using a pH testing kit. Hence, the independent or manipulated variable is THE NUMBER OF DAYS THE RAINWATER WAS ALLOWED TO SIT before measuring their pH.

sleep paralysis is a parasomnia, events associated with sleep.

sleep paralysis happens when you are in the middle of waking up or falling asleep. it is the feeling of being conscious but unable to move. it definitely involves hallucinations.

i had a friend that had sleep paralysis and he told me a story one time where he was laying in bed and he couldn't move his body no matter how hard he tried and there was someone standing in the corner of his room coming towards him. he couldn't move and you can't "wake up" because you are already conscious. sometimes sleep paralysis can be triggered by frequent waking up during the night based off of multiple trips to the bathroom, or if you had ever been abused, sleep paralysis can start happening from things like that.

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.