I really need it today :)

In which situation has the independent variable for the experiment been changed? check all that apply. changed from counting the number of duckweed at day 0 and day 14 to counting them every day changed from testing duckweed growth in beakers to testing duckweed growth in large outdoor tanks changed from testing the effect of ph on duckweed growth to testing the effect of light levels on duckweed growth changed from testing the effect of acid ph on duckweed growth to testing the effect of basic ph on duckweed growth

The velocity of sound wave in air at 35°c is 353m/s, calculate the velocity of sound at 46°c

Mrs. smith does her daily chores. she walks 5 m to the laundry room and then turns around and walks -14 m to the kitchen. the whole process takes her 11 minutes. what was her average velocity for these events? (choose more than 1) a. 1.48 m/s b. 0.212 m/s c. -0.136 m/s d. -0.0075 m/s