The Amount of a Certain Radioactive Isotope Present at Time $\mathrm { A } ( \mathrm { t } ) = 400 \mathrm { e } ^ { - 0.02664 \mathrm { t } }$

question 302

Multiple Choice

The amount of a certain radioactive isotope present at time t is given by $\mathrm { A } ( \mathrm { t } ) = 400 \mathrm { e } ^ { - 0.02664 \mathrm { t } }$ grams, where t is the time in years that the isotope decays. The initial amount present is 400 grams. How many grams remain
After 20 years? Round to the nearest hundredth.

• A) 681.48 g
• B) 234.78 g
• C) 379.25 g
• D) 397.87 g

Describe the mechanisms through which cytotoxic T cells target and attack intracellular pathogens.

Identify the primary antibody produced in response to an antigen and its importance.

Explain the process of antibody production and the cells involved in this process.

Differentiate between primary and secondary (memory) responses of the immune system.

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