Which of these conclusions is correct about the cities whose temperatures were measured by the students?
about 300 cities have an average monthly temperature of 60°c.
about 300 cities have an average monthly temperature of 20°c.
almost 50% of the cities have an average monthly temperature less than or equal to 35°c
almost 50% of the cities have an average monthly temperature less than or equal to 20°c.

If i had more info, id have a better answer. But based of luck and guessing, i am going to go with c) almost 50% of the cities have an average monthly temperature less than or equal to 35 degrees C.

The correct answer is "Almost 50% of the cities have an average monthly temperature less than or equal to 35°C".

Explanation:

The missing information of this question is as follows:

"A group of students measured the average monthly temperature of 1000 cities around the world and plotted the cumulative frequency graph shown below.

A cumulative frequency graph. The label for the x-axis reads 'Average monthly temperature (in degrees Celsius).' The label for the y-axis reads 'Cumulative Frequency (number of cities).' The coordinates that make up the shape of the line are as follows: (0, 0), (50, 10), (50, 20), (400, 30), (700, 40), (950, 50), (1000, 60), (1000, 70)".

As it can be noted by looking to the coordinate of the graph "(400, 30)", the number 400 represents the cumulative number of cities that have a temperature of at least 30 °C. Since the total number of cities is 1000, 400 cities is almost 50% of the total cities and the temperature of 30 °C less than 35°C.

the element that provides strength to the exoskeletons of clams and oysters is phosphorus.

this is so because calcium carbonate is the main component in the shells. calcium carbonate is strengthened by phosphorus.

explanation: