Which element makes a text's tone more casual?

a. correct sentences
b. terms of endearment
c. proper punctuation
d. slang

If both the president and the vice president can no longer serve, who will become the next head of state?

Nami conducts an investigation on plants. she places a grow light on a timer to give the plants different amounts of light to see if this would affect their growth. in this investigation, the amount of light is the .

The state fire marshal ensures a program can legally operate in a specific location and has sound structure?